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小学上册英语第六单元综合卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The chemical formula for table salt is __________.2.Which planet is known as the Red Planet?A. EarthB. VenusC. MarsD. Jupiter答案:C3.I like to play ________ (排球) with my classmates.4.My friend is a ______. He wants to be an astronaut.5. A __________ (电池) converts chemical energy into electrical energy.6.The bird sings a beautiful ______ (歌).7.Which organ is responsible for breathing?A. HeartB. LungsC. StomachD. Brain答案:b8.The Earth's crust is essential for supporting ______.9.What do you call the place where books are kept?A. LibraryB. MuseumC. SchoolD. Store答案: A10.What is the famous fairytale character known for leaving a glass slipper?A. CinderellaB. Snow WhiteC. BelleD. Rapunzel答案:A11.We play ________ (volleyball) at the beach.12. A ______ (温室) extends the growing season for many plants.13.The movie was _____ (funny/boring).14.The llama is known for its soft _________ (毛).15. A __________ is a small creature that often hides under rocks.16.The chemical symbol for platinum is ______.17.I have ________ friends at school.18.I can reflect on my experiences with my ________ (玩具名称).19.I like to _______ (参加) sports teams at school.20.The ______ of a flower is often colorful and fragrant. (花瓣通常颜色鲜艳且芳香。
高三英语心理学常识单选题40题1. What is the term for the study of the mind and behavior?A. PhysiologyB. PsychologyC. SociologyD. Anthropology答案：B。
选项A“Physiology”是生理学；选项B“Psychology”是心理学；选项C“Sociology”是社会学；选项D“Anthropology”是人类学。
题干问的是对心理和行为的研究的术语，所以是心理学。
2. Which of the following is an example of a cognitive process?A. SleepingB. EatingC. ThinkingD. Breathing答案：C。
选项A“Sleeping”是睡觉；选项B“Eating”是吃；选项C“Thinking”是思考；选项D“Breathing”是呼吸。
认知过程包括感知、注意、记忆、思维等，所以思考是认知过程的一个例子。
3. What does the term “consciousness” refer to?A. UnawarenessB. AwarenessC. SleepinessD. Tiredness答案：B。
选项A“Unawareness”是无意识；选项B“Awareness”是意识；选项C“Sleepiness”是困倦；选项D“Tiredness”是疲劳。
“consciousness”指的是意识。
4. Which psychological perspective emphasizes the role of unconscious processes?A. Behavioral perspectiveB. Cognitive perspectiveC. Psychodynamic perspectiveD. Humanistic perspective答案：C。
考前英语作文急救An Emergency Guide for English Essay Writing before Exams。
As the exam season approaches, many students find themselves scrambling to prepare for the various subjects, including English essay writing. While the pressure to perform well can be immense, it is essential to remember that with proper planning and execution, writing a compelling essay is not an impossible task. This guide aims to provide a comprehensive framework for students to follow in their essay writing journey, ensuring that they arewell-prepared for the exam.1. Understanding the Prompt。
The first step in writing an effective essay is to thoroughly understand the prompt. Read the instructions carefully and identify the key elements such as the topic, the required length, and any specific instructions orlimitations. Ensure that you have a clear understanding of what the essay is asking you to discuss and how you should approach it.2. Brainstorming and Outlining。
重庆“PEP”24年小学5年级上册英语第4单元暑期作业考试时间：90分钟（总分:120）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、听力题：The chemical symbol for antimony is __________.2、听力题：She is _____ (running) a marathon.3、听力题：The chemical formula for citric acid is ______.4、听力题：An example of a renewable energy source is ______ (solar) power.5、听力题：__________ are important for the growth of crops.6、填空题：The teacher gives _____ (评估) to check progress.7、填空题：The ________ (骑行路径) is safe and scenic.8、听力题：I see a _______ (hawk) flying above.9、填空题：_____ (阳光) helps plants make food through photosynthesis.10、听力题：The Mediterranean Sea is located between Europe and _______.11、听力题：The _____ (cabbage) is fresh.12、填空题：A rabbit's nose twitches when it is ________________ (警觉).13、What is the main ingredient in a Caesar salad?A. LettuceB. SpinachC. KaleD. Arugula14、填空题：Plants can be ______ (装饰) in homes.15、听力题：The __________ helps to create new cells in the body.16、听力题：An _______ is an atom that has a charge.17、听力题：The __________ is a well-known tourist attraction.18、听力题：The chemical formula for potassium carbonate is ______.19、填空题：The __________ (历史的比较) reveals similarities and differences.20、听力题：The school is very ________.21、填空题：I have a big _______ (名词) of toys. Each one brings back _______ (记忆).22、What is a common pet that purrs?A. DogB. CatC. FishD. Rabbit23、听力题：A solution that does not conduct electricity is called a _______ electrolyte.24、How many legs does a snail have?A. 6B. 8C. 0D. 1025、What do you call the process of changing from a liquid to a gas?A. EvaporationB. FreezingC. MeltingD. Condensation26、填空题：The ________ was a major event in the history of England.27、听力题：I want to ________ my toys.28、填空题：I have a great relationship with my ____.29、What instrument has keys and is played by pressing?A. GuitarB. DrumsC. PianoD. Flute30、填空题：A _____ (34) can be hot or cold.31、填空题：I like to solve ______ (难题) because it challenges my mind. It feels great when I find the solution.32、填空题：My favorite season is ______ (春天).33、填空题：I love to ______ (与他人分享) my creativity.34、填空题：We have ______ (课外活动) after school.35、填空题：Many plants have ______ (不同) shapes and sizes.The __________ is where seeds develop in a flower.37、Which planet is closest to the sun?A. EarthB. MercuryC. VenusD. Mars答案:B38、填空题：Recognizing the signs of a healthy plant can lead to better ______ practices. (识别健康植物的迹象可以促进更好的园艺实践。
如何救助断肢的人英语作文Title: Providing Aid to an Individual with an Amputation。
In emergency situations where individuals experience traumatic incidents leading to limb loss, it's crucial to provide immediate assistance to mitigate further harm and offer necessary medical care. Offering aid to someone with an amputation requires a combination of swift action, empathy, and knowledge. Here's a comprehensive guide on how to assist someone who has suffered an amputation:1. Assess the Situation: Upon encountering someone with an amputation, quickly assess the scene to ensure safetyfor both the victim and yourself. Check for any ongoing dangers such as fire, traffic, or further risks of injury.2. Call for Help: Dial emergency services immediately to summon professional medical assistance. Provide clear and concise information about the situation, including thelocation and the nature of the injury.3. Control Bleeding: Apply direct pressure to the wound using a clean cloth or bandage to control bleeding. Elevate the injured limb if possible to help reduce blood flow. Avoid using a tourniquet unless absolutely necessary and if you have been trained in its application.4. Comfort and Reassure: Stay calm and offer reassurance to the individual. Assure them that help is on the way and that they are not alone. Keep them warm by covering them with a blanket or jacket if needed.5. Address Shock: Traumatic incidents can induce shock, which may manifest as pale skin, rapid heartbeat, or altered mental state. Lay the person down, elevate their legs slightly, and cover them with a blanket to help maintain body temperature and alleviate shock symptoms.6. Handle the Amputated Limb: If the amputated limb is present, handle it with care. Wrap it in a clean, damp cloth, place it in a sealed plastic bag, and keep it coolby placing it in a container surrounded by ice or cold water. Do not directly apply ice to the severed limb.7. Provide Emotional Support: Coping with the immediate aftermath of an amputation can be emotionally overwhelming. Offer words of encouragement and support while respecting the individual's privacy and dignity.8. Stay with the Person: Until professional help arrives, remain with the individual to offer continuous support and monitor their condition for any changes. Reassure them that they are in good hands and that help is on its way.9. Communicate with Emergency Responders: When emergency medical services arrive, provide them with a clear account of the events leading up to the injury, any first aid measures you've administered, and any pertinent medical history if known.10. Follow-up Care: After the immediate crisis has been addressed, encourage the individual to seek follow-upmedical care and counseling to aid in their recovery process. Offer to assist them in making arrangements for ongoing support and rehabilitation services.In conclusion, providing aid to someone who has suffered an amputation requires a coordinated effort of prompt action, compassion, and knowledge. By following these steps, you can make a significant difference in the well-being and recovery of the individual in need.。
UNIT 5 FIRST AID Section Ⅳ Expanding Your World基础达标练Ⅰ.单句填空1.The children panicked （panic）when they realized they were lost.2. With the help of his friends and teachers, he got rid of the bad habit at last.3.The twin brothers bled （bleed）for their country and died without any regrets.4.Unemployment and the death of his wife drove him to desperation （desperate）.5.With a bad mood, she delayed （delay）the work that she didn’t want to perform.6.The mountain was bathed in warm sunshine, which was beautiful beyond words.7.The man justified （justify）his mistakes, which made all of us look down upon him.8.He found a coin in his pocket and slipped （slip）it into her collecting box.9.It was so foggy （fog）that we had to feel our way home.10.Tom dashed out the instant the helicopter landed and hugged Jane tightly （tight）.Ⅱ. 同义替换act as; delay; depends on; ease; out of shape1.Aspirin is a commonly used drug which can be taken to relieve discomfort. ease2.Because of the bad weather, all the flights have been put off. delayed3.A trained dog can serve as a guide to a blind person. act as4.Whether or not we can start off tomorrow relies on the weather. depends on5.I have been in poor health ever since I left the army. out of shapeⅢ. 完成句子1.正如你知道的，除了美味的饺子，敬老院里的老年人同样需要的是温暖和关心。
PRINCE2® 6th Edition Practitioner 1 Introduction1.1 The structure of PRINCE21.2 What PRINCE2 does not provide1.3 What makes a project a ‘PRINCE2 project’?1.4 The purpose of this manual2 Project management with PRINCE22.1 What is a project?2.2 What is project management?2.3 What is it we wish to control?2.4 What does a project manager do?2.5 Projects in context2.6 Applying PRINCE23 Principles3.1 Continued business justification3.2 Learn from experience3.3 Defined roles and responsibilities3.4 Manage by stages3.5 Manage by exception3.6 Focus on products3.7 Tailor to suit the project4 Tailoring and adopting PRINCE24.1 Tailoring PRINCE24.2 Adopting PRINCE24.3 Tailoring PRINCE2 to suit different projects4.4 Adopting PRINCE2 in an organizational environment5 Introduction to PRINCE2 themes5.1 Tailoring the themes5.2 Format of the theme chapters6 Business case6.1 The business case theme6.2 PRINCE2’s requirements for the business case6.3 Guidance for effective business case management6.4 Techniques: investment appraisal7 Organization7.1 The organization theme7.2 PRINCE2’s requirements for organization7.3 Guidance for effective project organization8 Quality8.1 The quality theme8.2 PRINCE2’s requirements for quality8.3 Guidance for effective quality management8.4 Technique: recommended quality review technique9 Plans9.1 The plans theme9.2 PRINCE2’s requirements f or the plans theme9.3 Guidance for effective planning9.4 Techniques: prioritization, estimation and scheduling10 Risk10.1 The risk theme10.2 PRINCE2’s requirements for risk management10.3 Guidance for effective risk management10.4 Technique: recommended risk management procedure11 Change11.1 The change theme11.2 PRINCE2’s approach to change11.3 Guidance for effective change control11.4 Technique: recommended issue and change control procedure12 Progress12.1 The progress theme12.2 PRINCE2’s requirements for managing progress12.3 Guidance for effective progress management12.4 Techniques: progress evaluation and peer review13 Introduction to processes13.1 The PRINCE2 journey13.2 The PRINCE2 process model13.3 Structure of the process chapters13.4 Tailoring the processes14 Starting up a project14.1 Purpose14.2 Objective14.3 Context14.4 Activities14.5 Tailoring guidelines15 Directing a project15.1 Purpose15.2 Objective15.3 Context15.4 Activities15.5 Tailoring guidelines16 Initiating a project16.1 Purpose16.2 Objective16.3 Context16.4 Activities16.5 Tailoring guidelines17 Controlling a stage17.1 Purpose17.2 Objective17.3 Context17.4 Activities17.5 Tailoring guidelines18 Managing product delivery18.1 Purpose18.2 Objective18.3 Context18.4 Activities18.5 Tailoring guidelines19 Managing a stage boundary19.1 Purpose19.2 Objective19.3 Context19.4 Activities19.5 Tailoring guidelines20 Closing a project20.1 Purpose20.2 Objective20.3 Context20.4 Activities20.5 Tailoring guidelines21 Considerations for organizational adoption 21.1 Tailoring PRINCE2 for an organization 21.2 Embedding PRINCE2 in the organization APPENDICESA Product description outlinesB Standards alignmentC Roles and responsibilitiesD Product-based planning exampleE Health check。
考点5-主旨要义之文章大意--练高考--心中有数1.2022年全国甲卷之C篇As Ginni Bazlinton reached Antarctica, she found herself greeted by a group of little Gentoo penguins (企鹅) longing to say hello. These gentle, lovely gatekeepers welcomed her and kick-started what was to be a trip Ginni would never forget.Ever since her childhood, Ginni, now 71, has had a deep love for travel. Throughout her career (职业) as a professional dancer, she toured in the UK, but always longed to explore further. When she retired from dancing and her sons eventually flew the nest, she decided it was time to take the plunge.After taking a degree at Chichester University in Related Arts, Ginni began to travel the world, eventually getting work teaching English in Japan and Chile. And it was in Chile she discovered she could get last-minute cheap deals on ships going to Antarctica from the islands off Tierra del Fuego, the southernmost tip of the South American mainland. “I just decided I wanted to go,” she says. “I had no idea about what I’d find there and I wasn’t nervous, I just wanted to do it. And I wanted to do it alone as I always prefer it that way.”In March 2008, Ginni boarded a ship with 48 passengers she’d never met before, to begin the journey towards Antarctica. “From seeing the wildlife to witness ing sunrises, the whole experience was amazing. Antarctica left an impression on me that no other place has,” Ginni says. “I remember the first time I saw a humpback whale; it just rose out of the water like some prehistoric creature and I thought it was smiling at us. You could still hear the operatic sounds it was making underwater.”The realization that this is a precious land, to be respected by humans, was one of the biggest things that hit home to Ginni.28. Which of the following best explains “take the plunge” underlined in paragraph 2?A. Try challenging things.B. Take a degree.C. Bring back lost memories.D. Stick to a promise.29. What made Ginni decide on the trip to Antarctica?A. Lovely penguins.B. Beautiful scenery.C. A discount fare.D. A friend’s invitation.30. What does Ginni think about Antarctica after the journey?A. It could be a home for her.B. It should be easily accessible.C It should be well preserved. D. It needs to be fully introduced.31. What is the text mainly about?A. A childhood dream.B. An unforgettable experience.C. Sailing around the world.D. Meeting animals in Antarctica.【答案】28. A 29. C 30. C 31. B【解析】本文是一篇说明文。
大学英语六级考试模拟试卷七十九(总分：100.00，做题时间：130分钟)Listening Comprehension(总题数：0，分数：0.00)Section A(总题数：8，分数：0.00).Questions 1 to 4 are based on the conversation you have just heard.1.（分数：16.00）A.He wants the woman to explain her major.B.The woman is from a famous university.C.The woman's major is irrelevant to a tour guide.√D.He is also from the university.解析：[听力原文]M: It says here that you graduated from University of Pennsylvania with a major in philosophy.W: Right. Then you may think I am not fit for this job according to my educational background. But I want to be a tour guide very much because I like travelling and meeting various kinds of people. So I took an evening course at the Tourism School after graduation and I have gotten a qualification certificate.M: What do you think are the responsibilities of a tour guide?W: A tour guide must be responsible for arranging and coordinating tour activities, and offering services of transportation, accommodation, sightseeing, shopping and entertainment.M: Then I want to ask you some questions about emergencies. If there is an accident—for example a tourist falls ill—what would you do?W: I think I will call the office to send someone to meet us, and escort that person to the nearest hospital without interrupting our trip.M: If one of them forgot a camera in a restaurant, would you let the tourist bus go back?W: In fact, prior to their boarding the bus and their getting off the bus, I will make an announcement to remind them that they should check their belongings.M: Well, it seems that you have all the practical experience to handle these cases. Is there anything you want to ask about?W: I'd like to be an overseas tour guide someday. Would there ever be any chance of that?M: Certainly. But in a few years, after you learn more about our business, you may go overseas with a tour group.Why does the man refer to the woman's education?.Questions 5 to 8 are based on the conversation yon have just heard.5.（分数：16.00）A.Developing various applications.B.Expanding foreign markets for his materials.C.Producing leisure shoes with different materials.√D.Promoting the quality of his leisure dress.解析：[听力原文]W: OK, I've got all the paperwork here for your application. Everything seems to be in order. Let's just have a look at your business plan. Perhaps you could tell me about your ideas?M: Yes, of course. We plan to make leisure shoes, from various materials. At the moment, we've only got a couple of styles for young girls and boys, but we want to expand our range to include more styles.W: You say that you've got some styles. Have you already started promoting and selling your shoes?M: Only on a small scale, but they're selling really well and we receive some support from the students.W: Right, so why exactly do you want a loan? Are you going to expand your range or increase your production?M: Well, both, we hope.W: And how do you plan to sell the shoes? Direct to the public?M: No, we're going to sell through other ways. You know, in supermarkets, at outlets on campus and by online stores. We've already had talks with a company that runs the "Travel" chain. They are going to stock our shoes in their main outlets.W: OK, what about your market? Who do you think is going to be your main market?M: So far most of our customers have been young people—you know, students, teenagers, people who are interested in sports. Most of them like the healthy and natural life. So we're going to try to consolidate that market. I don't want to change our strategy at the moment.What is the man's business plan?Section B(总题数：7，分数：0.00).Questions 9 to 12 are based on the passage you have just heard.1.（分数：16.00）A.Cook the milk automatically.B.Send the milk back to the supermarket.C.Place the milk to the front of the shelf.√D.Order fresh milk to replace this one.解析：[听力原文]A refrigerator of the future that tells you what to cook with your leftovers and automatically reorders fresh food is being designed in the UK. The self-cleaning "refrigerator of the future" will automatically place supermarket-home delivery orders when required and move food near its use by date to the front of the shelves. Researchers hope the fridge could clean itself, cut down on wasted food and offer up recipes—which could be tailored to different countries, cuisine and seasons. With Brits putting in 36 million hours every year of free overtime—leaving little time for household chores—the refrigerator could help save precious time during modern-day lives. These new developments are in the pipeline thanks to collaborations between scientists at the university and the online supermarket Ocado. The planned new features include the ability for refrigerators to scan their shelves to see what is in stock and use this information to both plan meals andautomatically place a supermarket food order. The smart fridge will use "nano-articulated technology" shelf surfaces which will accomplish products which soon need to be eaten to the front of the refrigerator. Ultrasound-scanning technology built into the door will allow the refrigerator to "swipe and capture" the food on a plate before and after mealtime, meaning it can assess what type and amount of food is wasted. Cookbooks are essentially inventory lists of food items. The key concept in the successful implementation of this process is accurate inventory tracking.How will a future refrigerator deal with the milk that is near its sell-by date?.Questions 13 to 15 are based on the passage you have just heard.5.（分数：12.00）A.A phenomenon of an aging face because of people facing a computer for a long time.√B.A feature of a screen-shape face because of people following fashion on the Internet.C.A symptom of a "turkey neck" because of people imitating the turkey.D.A representation of wrinkles because of people lifting their heads for long hours.解析：[听力原文]A growing number of women are developing something called a "computer face," a leading cosmetic surgeon said. Dr. Prager said professionals who worked long hours in front of a screen were ending up with loose skin, a "turkey neck" and deep-set wrinkles on their forehead and around their eyes. The specialist said that, of all his clients, office workers were most likely to show premature signs of ageing. If you are one of the unfortunate people who frown or squint when they are concentrating on the screen, then over time, you will inevitably end up with frown lines. What is perhaps more surprising is the number of women with loose jaws because they are sitting in one position for too long. If you spend most of the time looking down then the neck muscles shorten and go loose, eventually giving you a second neck. We are seeing a lot of women who work in executive jobs in offices who have this problem. Dr. Prager, who has a practice near Harley Street in London, said he encourages his clients to put a mirror next to their computer so they can see if they are frowning at the screen. A generation of younger men and women who had grown up with information technology were developing the "computer face" at a much earlier age. Dr. Prager said there were several simple steps which could avoid the computer face such as regular screen breaks and stretching the neck muscles.What is called a "computer face"?Section C(总题数：10，分数：0.00).Questions 16 to 19 are based on the recording you have just heard.1.（分数：16.00）A.They teach them valuable lessons.√B.They are more important than presents.C.They teach them to survive pains.D.They are as interesting as journeys.解析：[听力原文]Some people choose to tightly grasp the past and stay stuck in their story, playing it over and over like a broken record. They, in turn, live with regret, anger, fear and resentment.Those who choose to live life with no regrets let go off the past and live joyfully in the present moment. They know that every experience gives birth to lessons and growth, even if it felt painful at the time. They look at all life experiences, both positive and negative, as part of their divine journeys. They forgive themselves and others and understand their power is always in the present moment. They are grateful and optimistic, and know whatever they focus their thoughts on is what they attract. They also live by the following important mindsets.We all have unique gifts and talents we bring to this earth, accompanied by our distinct personality. We also have a life purpose to pursue—whether it's to inspire, create, support, protect, or teach. If you pave your own path by following your passions and inner guidance, your life will take on deeper meaning and fulfillment. If you pave your own path with what society and others expect of you, you'll waste your precious time creating a life of pain, resentment, and regret. Instead of living a life of what you think you should do, try living according to what your inner knowing guides you to do.We all know the feeling of being passionate about something. Our eyes light up, our energy increases, we smile, feel fulfilled, in the present, and deeply connected to what we are doing. Too often we allow the pressures of society and fear to steer us into spending our days engaged in activities we feel we should do. Whether it's working in an unsatisfying job, staying in a bad relationship, or worrying what others think, none of those behaviors serve our higher good. To check whether your passions are guiding your life, write a list of up to 10 experiences you've had in your life where you felt the most fulfilled and connected. Then assess how many of these activities you have done in the past twelve months. If it's not many, then start to reduce the amount of things you feel you have to do and start doing more of what you want to do.How do positive people think about their past experiences?.Questions 20 to 22 are based on the recording you have just heard.5.（分数：12.00）A.It can alleviate some stress.√B.It can improve our memories.C.It can help us gain self-comfort.D.It can help us get a high mark.解析：[听力原文]With exams, quizzes, essays, projects, and myriad deadlines for different things, effective study habits are critical for keeping stress at bay during college. Having these great study habits can make things easier and alleviate some of the stress looming overhead. If you are in need of a bit of an improvement, or just want to get some new ideas, develop study habits that you should be practicing.Flashcards are designed to promote active memory recall of information. Byusing flashcards with a question or term on one side and the answer or the definition on the other, you will force your brain to recall the necessary information. Even if you struggle a bit with a card, you will still be actively reviewing the necessary material.One of the other reasons why flashcards are effective is that they utilize spaced repetition learning techniques. Spaced repetition has been proven time and gain to be one of the most effective ways of building up memory and increasing recall of information. By studying the information again and again, at spaced intervals, you will be able to recall the information faster and far more easily.Many students put off studying until just before the exam, with the more diligent students giving themselves a week or two prior to a test. While this may sound effective and like a good manner of planning, it's actually an ineffective method of preparing and studying. It's best to revise the information a little bit every day, so that you are not overwhelmed when a test or pop quiz comes around.One method of revising is to make a mind-map. This is a bit like a flow chart—in that you start with one core concept in the center, and then branch off into connected sections. This will help you to connect everything together and associate the terms with one another. When it comes time to take the exam, you will be better prepared and the key terms will jump out at you.Read aloud to yourself and, as silly as it may seem, pretend you are teaching a student. Read your notes aloud; pretend you are lecturing. Do this over and over, until you no longer have to look at your notes. Once you have accomplished that, do it again.Take one of the main concepts and turn it into a little story. Make sure you are able to explain this concept, no matter how complex it actually is, to someone who has never heard of it before.What is the benefit of having great study habits?.Questions 23 to 25 are based on the recording you have just heard.8.（分数：12.00）A.The ones that trigger memories or opinions.√B.The ones that make others feel surprised.C.The ones which you can talk a lot about.D.The ones that can be discussed for a long time.解析：[听力原文]In a world where technology is increasing our capacity to connect with people worldwide, it is also diminishing our ability to effectively connect with people in person. Just like learning how to cook, develop software, or play a sport, the ability to connect with others is a skill and you can learn how to do it more effectively. Learning the social skills necessary to connect with others will help you be more successful in every aspect of your life. Here are some social skills you can develop to be more charismatic:Those who are great with people don't necessarily have the gift-of-gab, but rather, are great at asking questions. One of the most important social skills you can develop is the ability to ask questions; not in an interrogating way, but in the way that will help you understand people better and strengthen your relationship withthem. People love talking about themselves, so asking questions that trigger memories (i. e. "What was it like for you when...?"), cause them to give their opinion (i. e. "What do you think about...?"), or ask for advice (i. e. "I have a dilemma and would love your thoughts...?"), will put you in the driver's seat by allowing them to be the center of the conversation.When someone shares great news with you, instead of dismissing it, sharing good news of your own, or even bashing their good news—celebrate their win by being genuinely excited for them.For many, the group setting is the perfect opportunity to pull back, check their phone, and zone out of the conversation—but not you. Pay close attention in a group setting, you'll be able to learn how to connect with others by what they say, how they say it, and even what people choose not to say. Be aware of who likes to lead the conversation, what people like to talk about, and if someone is being excluded from the conversation.On a daily basis you are bombarded with distractions competing for one of your most precious resources—your attention. Making eye contact with the person you are speaking with face to face is an outward expression that you are confident and fully engaged with that person. However, if someone isn't making eye contact with you, before you jump to conclusions, be aware that it may be culturally unacceptable for them to do so, they are intimidated by you, or it makes them uncomfortable.Which kind of questions help with communicating?。
A Practitioner’s Guide toEstimation of Random-Coef cientsLogit Models of DemandAviv NevoUniversity of California–Berkeley,Berkeley,CA94720-3880andNBEREstimation of demand is at the heart of many recent studies that exam-ine questions of market power,mergers,innovation,and valuation of new brands in differentiated-products markets.This paper focuses on one of the main methods for estimating demand for differentiated products:random-coef cients logit models.The paper carefully discusses the latest innovations in these methods with the hope of increasing the understanding,and there-fore the trust among researchers who have never used them,and reducing the dif culty of their use,thereby aiding in realizing their full potential.1.IntroductionEstimation of demand has been a key part of many recent studies examining questions regarding market power,mergers,innovation, and valuation of new brands in differentiated-product industries.1 This paper explains the random-coef cients(or mixed)logit method-ology for estimating demand in differentiated-product markets usingAn earlier version of this paper circulated under the title“A Research Assistant’s Guide to Random Coef cients Discrete Choice Model of Demand.”I wish to thank Steve Berry, Iain Cockburn,Bronwyn Hall,Ariel Pakes,various lecture and seminar participants, and an anonymous referee for comments,discussions,and suggestions.Financial sup-port from the UC Berkeley Committee on Research Junior Faculty Grant is gratefully acknowledged.1.Just to mention some examples,Bresnahan(1987)studies the1955price war in the automobile industry;Gasmi et al.(1992)empirically study collusive behavior in a soft-drink market;Hausman et al.(1994)study the beer industry;Berry et al.(1995,1999) examine equilibrium in the automobile industry and its implications for voluntary trade restrictions;Goldberg(1995)uses estimates of the demand for automobiles to investi-gate trade policy issues;Hausman(1996)studies the welfare gains generated by a new brand of cereal;Berry et al.(1996)study hubs in the airline industry;Bresnahan et al. (1997)study rents from innovation in the computer industry;Nevo(2000a,b)examines price competition and mergers in the ready-to-eat cereal industry;Davis(1998)studies spatial competition in movie theaters;and Petrin(1999)studies the welfare gains from the introduction of the minivan.©2000Massachusetts Institute of Technology.Journal of Economics&Management Strategy,V olume9,Number4,Winter2000,513–548514Journal of Economics&Management Strategy market-level data.This methodology can be used to estimate the dem-and for a large number of products using market data and allowing for the endogenity of price.While this method retains the bene ts of alternative discrete-choice models,it produces more realistic demand elasticities.With better estimates of demand,we can,for example,bet-ter judge market power,simulate the effects of mergers,measure the bene ts from new goods,or formulate innovation and competition policy.This paper carefully discusses the recent innovations in these methods with the intent of reducing the barriers to entry and increas-ing the trust in these methods among researchers who are not familiar with them.Probably the most straightforward approach to specifying de-mand for a set of closely related but not identical products is to specify a system of demand equations,one for each product.Each equation speci es the demand for a product as a function of its own price,the price of other products,and other variables.An example of such a system is the linear expenditure model(Stone,1954),in which quan-tities are linear functions of all prices.Subsequent work has focused on specifying the relation between prices and quantities in a way that is both exible(i.e.,allows for general substitution patterns)and con-sistent with economic theory.2Estimating demand for differentiated products adds two addi-tional nontrivial concerns.The rst is the large number of products, and hence the large number of parameters to be estimated.Con-sider,for example,a constant-elasticity or log–log demand system, in which logarithms of quantities are linear functions of logarithms of all prices.Suppose we have100differentiated products;then without additional restrictions this implies estimating at least10,000param-eters(100demand equations,one for each product,with100prices in each).Even if we impose symmetry and adding up restrictions, implied by economic theory,the number of parameters will still be too large to estimate them.The problem becomes even harder if we want to allow for more general substitution patterns.An additional problem,introduced when estimating demand for differentiated products,is the heterogeneity in consumer tastes:If all consumers are identical,then we would not observe the level of dif-ferentiation we see in the marketplace.One could assume that pref-erences are of the right form[the Gorman form:see Gorman(1959)], so that an aggregate,or average,consumer exists and has a demand function that satis es the conditions speci ed by economic theory.32.Examples include the Rotterdam model(Theil,1965;Barten,1966),the translog model(Christensen et al.,1975),and the almost ideal demand system(Deaton and Muellbauer,1980).3.For an example of a representative consumer approach to demand for differenti-ated products see Dixit and Stiglitz(1977)or Spence(1976).Random-Coef cients Logit Models of Demand515 However,the required assumptions are strong and for many applicati-ons seem to be empirically false.The difference between an aggregate model and a model that explicitly re ects individual heterogeneity can have profound affects on economic and policy conclusions.The logit demand model(McFadden,1973)4solves the dimen-sionality problem by projecting the products onto a space of charac-teristics,making the relevant size the dimension of this space and not the square of the number of products.A problem with this model is the strong implication of some of the assumptions made.Due to the restrictive way in which heterogeneity is modeled,substitution between products is driven completely by market shares and not by how similar the products are.Extensions of the basic logit model relax these restrictive assumptions,while maintaining the advantage of the logit model in dealing with the dimensionality problem.The essen-tial idea is to explicitly model heterogeneity in the population and estimate the unknown parameters governing the distribution of this heterogeneity.These models have been estimated using both market-and individual-level data.5The problem with the estimation is that it treats the regressors,including price,as exogenously determined.This is especially problematic when aggregate data is used to estimate the model.This paper describes recent developments in methods for esti-mating random-coef cients discrete-choice models of demand[Berry, 1994;Berry et al.,1995(henceforth BLP)].The new method maintains the advantage of the logit model in handling a large number of prod-ucts.It is superior to prior methods because(1)the model can be estimated using only market-level price and quantity data,(2)it deals with the endogeneity of prices,and(3)it produces demand elasticities that are more realistic—for example,cross-price elasticities are larger for products that are closer together in terms of their characteristics.The rest of the paper is organized as follows.Section2describes a model that encompasses,with slight alterations,the models pre-viously used in the literature.The focus is on the various modeling assumptions and their implications for estimation and the results.In Section3I discuss estimation,including the data required,an outline of the algorithm,and instrumental variables.Many of the nitty-gritty details of estimation are described in an appendix(available from4.A related literature is the characteristics approach to demand,or the address approach(Lancaster,1966,1971;Quandt,1968;Rosen,1974).For a recent exposition of it and a proof of its equivalence to the discrete choice approach see Anderson et al.5.For example,the generalized extreme-value model(McFadden,1978)and the random-coef cients logit model(Cardell and Dunbar,1980;Boyd and Mellman,1980; Tardiff,1980;Cardell,1989;and references therein).The random-coef cients model is often called the hedonic demand model in this earlier literature;it should not be con-fused with the hedonic price model(Court,1939;Griliches,1961).516Journal of Economics&Management Strategy /nevo).Section4provides a brief example of the type of results the estimation can produce.Section5concludes and discusses various extensions and alternatives to the method de-scribed here.2.The ModelIn this section I discuss the model with an emphasis on the vari-ous modeling assumptions and their implications.In the next section I discuss the estimation details.However,for now I want to stress two points.First,the method I discuss here uses(market-level)price and quantity data for each product,in a series of markets,to estimate the model.Some information regarding the distribution of consumer characteristics might be available,but a key bene t of this methodol-ogy is that we do not need to observe individual consumer purchase decisions to estimate the demand parameters.6Second,the estimation allows prices to be correlated with the econometric error term.This will be modeled in the following way.A product will be de ned by a set of characteristics.Producers and consumers are assumed to observe all product characteristics.The researcher,on the other hand,is assumed to observe only some of the product characteristics.Each product will be assumed to have a char-acteristic that in uences demand but that either is not observed by the researcher or cannot be quanti ed into a variable that can be included in the analysis.Examples are provided below.The unobserved charac-teristics will be captured by the econometric error term.Since the pro-ducers know these characteristics and take them into account when setting prices,this introduces the econometric problem of endogenous prices.7The contribution of the estimation method presented below is to transform the model in such a way that instrumental-variable methods can be used.2.1The SetupAssume we observe t1,...,T markets,each with i1,...,I t consumers.For each such market we observe aggregate quantities,6.If individual decisions are observed,the method of analysis differs somewhat from the one presented here.For clarity of presentation I defer discussion of this case to Section5.7.The assumption that when setting prices rms take account of the unobserved (to the econometrician)characteristics is just one way to generate correlation between prices and these unobserved variables.For example,correlation can also result from the mechanics of the consumer’s optimization problem(Kennan,1989).Random-Coef cients Logit Models of Demand 517average prices,and product characteristics for J products.8The de -nition of a market will depend on the structure of the data.BLP use annual automobile sales over a period of twenty years,and therefore de ne a market as the national market for year t ,where t 1,...,20.On the other hand,Nevo (2000a)observes data in a cross section of cities over twenty quarters,and de nes a market t as a city–quarter combination,with t 1,...,1124.Yet a different example is given by Das et al.(1994),who observe sales for different income groups,and de ne a market as the annual sales to consumers of a certain income level.The indirect utility of consumer i from consuming product j in market t ,U (x jt ,»jt ,p jt ,¿i ;),9is a function of observed and unobser-ved (by the researcher)product characteristics,x j t and »jt respectively;price,p jt ;individual characteristics,¿i ;and unknown parameters,.I focus on a particular speci cation of this indirect utility,10u ijt i (y ip jt )x jt i »j t ij t ,i 1,...,I t ,j 1,...,J ,t 1,...,T ,(1)where y i is the income of consumer i ,p jt is the price of product j in market t ,x j t is a K -dimensional (row)vector of observable character-istics of product j ,»j t is the unobserved (by the econometrician)prod-uct characteristic,and ij t is a mean-zero stochastic term.Finally,i is consumer i ’s marginal utility from income,and i is a K -dimensional (column)vector of individual-speci c taste coef cients.Observed characteristics vary with the product being considered.BLP examine the demand for cars,and include as observed charac-teristics horsepower,size and air conditioning.In estimating demand for ready-to-eat cereal Nevo (2000a)observes calories,sodium,and ber content.Unobserved characteristics,for example,can include the impact of unobserved promotional activity,unquanti able factors (brand equity),or systematic shocks to demand.Depending on the structure of the data,some components of the unobserved characteris-tics can be captured by dummy variables.For example,we can model »jt »j »t »j t and capture »j and »t by brand-and market-speci c dummy variables.Implicit in the speci cation given by equation (1)are three things.First,this form of the indirect utility can be derived from a8.For ease of exposition I have assumed that all products are offered to all con-sumers in all markets.The methods described below can easily deal with the case where the choice set differs between markets and also with different choice sets for different consumers.9.This is sometimes called the conditional indirect utility,i.e.,the indirect utility conditional on choosing this option.10.The methods discussed here are general and with minor adjustments can deal with different functional forms.518Journal of Economics &Management Strategy quasilinear utility function,which is free of wealth effects.For some products (for example,ready-to-eat cereals)this is a reasonable ass-umption,but for other products (for example,cars)it is an unreason-able one.Including wealth effects alters the way the term y i p jt enters equation (1).For example,BLP build on a Cobb-Douglas utility func-tion to derive an indirect utility that is a function of log (y i p jt ).In principle,we can include f (y i p jt ),where f ()is a exible functional form (Petrin,1999).Second,equation (1)speci es that the unobserved characteristic,which among other things captures the elements of vertical product differentiation,is identical for all consumers.Since the coef cient on price is allowed to vary among individuals,this is consistent with the theoretical literature of vertical product differentiation.An alter-native is to model the distribution of the valuation of the unobserved characteristics,as in Das et al.(1994).As long as we have not made any distributional assumptions on consumer-speci c components (i.e.,anything with subscript i ),their model is not more general.Once we make such assumptions,their model has slightly different implica-tions for some of the normalizations usually made.An exact discus-sion of these implications is beyond the scope of this paper.Finally,the speci cation in equation (1)assumes that all con-sumers face the same product characteristics.In particular,all con-sumers are offered the same price.Depending on the data,if different consumers face different prices,using either a list or average trans-action price will lead to measurement error bias.This just leads to another reason why prices might be correlated with the error term and motivates the instrumental-variable procedure discussed below.11The next component of the model describes how consumer pref-erences vary as a function of the individual characteristics,¿i .In the context of equation (1)this amounts to modeling the distribution of consumer taste parameters.The individual characteristics consist of two components:demographics,which I refer to as observed ,and additional characteristics,which I refer to as unobserved ,denoted D i and v i respectively.Given that no individual data is observed,neither component of the individual characteristics is directly observed in the choice data set.The distinction between them is that even though we do not observe individual data,we know something about the distri-bution of the demographics,D i ,while for the additional characteris-tics,v i ,we have no such information.Examples of demographics are income,age,family size,race,and education.Examples of the type of11.However,as noted by Berry (1994),the method proposed below can deal with measurement error only if the variable measured with error enters in a restrictive ly ,it only enters the part of utility that is common to all consumers,j in equation(3)below.Random-Coef cients Logit Models of Demand519 information we might have is a large sample we can use to estimate some feature of the distribution(e.g.,we could use Census data to estimate the mean and standard deviation of income).Alternatively, we might have a sample from the joint distribution of several demo-graphic variables(e.g.,the Current Population Survey might tell us about the joint distribution of income,education,and age in differ-ent cities in the US).The additional characteristics,i,might include things like whether the individual owns a dog,a characteristic that might be important in the decision of which car to buy,yet even very detailed survey data will usually not include this fact.Formally,this will be modeled asi i ÕDiåi,iP(),DiÃPD(D),(2)where Di is a d1vector of demographic variables,icaptures theadditional characteristics discussed in the previous paragraph,P()isa parametric distribution,PD ()is either a nonparametric distributionknown from other data sources or a parametric distribution with the parameters estimated elsewhere,Õis a(K1)´d matrix of coef cientsthat measure how the taste characteristics vary with demographics, andåis a(K1)(K1)matrix of parameters.12If we assume that P()is a standard multivariate normal distribution,as I do in the example below,then the matrixåallows each component ofi to have a different variance and allows for correlation between thesecharacteristics.For simplicity I assume that i and D i are indepen-dent.Equation(2)assumes that demographics affect the distribution of the coef cients in a fairly restrictive linear way.For those coef -cients that are most important to the analysis(e.g.,the coef cients on price),relaxing the linearity assumption could have important impli-cations[for example,see the results reported in Nevo(2000a,b)].As we will see below,the way we model heterogeneity has strong implications for the results.The advantage of letting the tasteparameters vary with the observed demographics,Di is twofold.First,it allows us to include additional information,about the distribution of demographics,in the analysis.Furthermore,it reduces the reliance on parametric assumptions.Therefore,instead of letting a key element of the method,the distribution of the random coef cients,be deter-mined by potentially arbitrary distributional assumptions,we bring in additional information.12.To simplify notation I assume that all characteristics have random coef cients. This need not be the case.I return to this in the appendix,when I discuss the details of estimation.520Journal of Economics &Management StrategyThe speci cation of the demand system is completed with the introduction of an outside good :the consumers may decide not to pur-chase any of the brands.Without this allowance,a homogenous price increase (relative to other sectors)of all the products does not change quantities purchased.The indirect utility from this outside option isu i 0t i y i »0t ¼0D i ¾0v i 0i 0t .The mean utility from the outside good,»0t ,is not identi ed (with-out either making more assumptions or normalizing one of the inside goods).Also,the coef cients ¼0and ¾0are not identi ed separately from coef cients on an individual-speci c constant term in equation (1).The standard practice is to set »0t ,¼0,and ¾0to zero,and since the term i y i will eventually vanish (because it is common to all prod-ucts),this is equivalent to normalizing the utility from the outside good to zero.Let (1,2)be a vector containing all the parameters of the model.The vector 1(,)contains the linear parameters,and the vector 2(Õ,å)the nonlinear parameters.13Combining equations (1)and (2),we haveu ijt i y ijt (x jt ,p j t ,»j t ;1)u ijt (x jt ,p jt ,v i ,D i ;2)ijt ,jt x jt p jt »jt ,u ijt [p j t ,x j t ](ÕD i åi ),(3)where [p j t ,x jt ]is a 1(K 1)(row)vector.The indirect utility is now expressed as a sum of three (or four)terms.The rst term,i y i ,is given only for consistency with equation (1)and will van-ish,as we will see below.The second term,jt ,which is referred to as the mean utility,is common to all consumers.Finally,the last two terms,ijt ijt ,represent a mean-zero heteroskedastic devia-tion from the mean utility that captures the effects of the random coef cients.Consumers are assumed to purchase one unit of the good that gives the highest utility.14Since in this model an individual is de-13.The reasons for the names will become apparent below.14.A comment is in place here about the realism of the assumption that consumers choose no more than one good.We know that many households own more than one car,that many of us buy more than one brand of cereal,and so forth.We note that even though many of us buy more than one brand at a time,less actually consume more than one at a time.Therefore,the discreteness of choice can be sometimes defended by de ning the choice period appropriately.In some cases this will still not be enough,in which case the researcher has one of two options:either claim that the above model is an approximation,or reduced-form,to the true choice model,or model the choice of multiple products,or continuous quantities,explicitly [as in Dubin and McFadden (1984)or Hendel (1999)].Random-Coef cients Logit Models of Demand521 ned as a vector of demographics and product-speci c shocks,(Di ,i,i0t,...,iJt),this implicitly de nes the set of individualattributes that lead to the choice of good j.Formally,let this set beAj t (x t,p t,t;2)©(D i,v i,i0t,...,iJ t)|u ij t u iltl0,1,...,Jª,where x t(x lt,...,x J t),p t(p lt,...,p J t),and t(lt,...,J t) are observed characteristics,prices,and mean utilities of all brands, respectively.The set A jt de nes the individuals who choose brand j in market t.Assuming ties occur with zero probability,the market share of the j th product is just an integral over the mass of consumers in the region Ajt.Formally,it is given bys jt(x t,p t,t;2)HA jtdP(D,v,)H A jt dP(|D,)dP(|D)dPD(D)HA jtdP()dP()dÃP D(D),(4)where P()denotes population distribution functions.The second equality is a direct application of Bayes’rule,while the last is a con-sequence of the independence assumptions previously made.Given assumptions on the distribution of the(unobserved)indi-vidual attributes,we can compute the integral in equation(4),either analytically or numerically.Therefore,for a given set of parameters equation(4)predicts of the market share of each product in each market,as a function of product characteristics,prices,and unknown parameters.One possible estimation strategy is to choose parame-ters that minimize the distance(in some metric)between the mar-ket shares predicted by equation(4)and the observed shares.This estimation strategy will yield estimates of the parameters that deter-mine the distribution of individual attributes,but it does not account for the correlation between prices and the unobserved product char-acteristics.The method proposed by Berry(1994)and BLP,which is presented in detail in the Section3,accounts for this correlation.2.2Distributional AssumptionsThe assumptions on the distribution of individual attributes made in order to compute the integral in equation(4)have important impli-cations for the own-and cross-price elasticities of demand.In this section I discuss some possible assumptions and their implications.522Journal of Economics &Management StrategyPossibly the simplest distributional assumption one can make in order to evaluate the integral in equation (4)is that consumer hetero-geneity enters the model only through the separable additive random shock,ij t .In our model this implies 20,or i and i for all i ,and equation (1)becomesu ijt (y ip jt )x jt »j t ijt ,i 1,...,I t ,j 1,...,J ,t 1,...,T .(5)At this point,before we specify the distribution of ij t ,the model described by equation (5)is as general as the model given in equation (1).15Once we assume that ij t is i.i.d.,then the implied sub-stitution patterns are severely restricted,as we will see below.If we also assume that ijt are distributed according to a Type I extreme-value distribution,this is the (aggregate)logit model.The market share of brand j in market t ,de ned by equation (4),iss j t exp (x jt p jt »jt )1k 1exp (x kt p kt kt ).(6)Note that income drops out of this equation,since it is common to all options.Although the model implied by equation (5)and the extreme-value distribution assumption is appealing due to its tractability,it restricts the substitution patterns to depend only on the market shares.The price elasticities of the market shares de ned by equation (6)are ´jkt @s j t p kt @p kt j t (p j t (1s jt )if j k ,p kt s kt otherwise.There are two problems with these elasticities.First,since in most cases the market shares are small,the factor (1s jt )is nearly constant;hence,the own-price elasticities are proportional to own price.Therefore,the lower the price,the lower the elasticity (in abso-lute value),which implies that a standard pricing model predicts a higher markup for the lower-priced brands.This is possible only if the marginal cost of a cheaper brand is lower (not just in absolute value,but as a percentage of price)than that of a more expensive product.For some products this will not be true.Note that this problem is a direct implication of the functional form in price.If,for example,indirect utility was a function of the logarithm of price,rather than price,then the implied elasticity would be roughly constant.In other15.To see this compare equation (5)with equation (3).words,the functional form directly determines the patterns of own-price elasticity.An additional problem,which has been stressed in the literature,is with the cross-price elasticities.For example,in the context of RTE cereals the cross-price elasticities imply that if Quaker CapN Crunch (a childern’s cereal)and Post Grape Nuts (a wholesome simple nutri-tion cereal)have similar market shares,then the substitution from General Mills Lucky Charms (a children’s cereal)toward either of them will be the same.Intuitively,if the price of one children’s cereal goes up,we would expect more consumers to substitute to another children’s cereal than to a nutrition cereal.Yet,the logit model restricts consumers to substitute towards other brands in proportion to market shares,regardless of characteristics.The problem in the cross-price elasticities comes from the i.i.d.structure of the random shock.In order to understand why this is the case,examine equation (3).A consumer will choose a product either because the mean utility from the product,jt ,is high or because the consumer-speci c shock,ijt ij t ,is high.The distinction becomes important when we consider a change in the environment.Consider,for example,the increase in the price of Lucky Charms discussed in the previous paragraph.For some consumers who previously con-sumed Lucky Charms,the utility from this product decreases enough so that the utility from what was the second choice is now higher.In the logit model different consumers will have different rankings of the products,but this difference is due only to the i.i.d.shock.There-fore,the proportion of these consumers who rank each brand as their second choice is equal to the average in the population,which is just the market share of the each product.In order to get around this problem we need the shocks to util-ity to be correlated across brands.By generating correlation we pre-dict that the second choice of consumers that decide to no longer buy Lucky Charms will be different than that of the average con-sumer.In particular,they will be more likely to buy a product with a shock that was positively correlated to Lucky Charms,for example CapN Crunch.As we can see in equation (3),this correlation can be generated either through the additive separable term ij t or through the term ij t ,which captures the effect the demographics,D i and v i .Appropriately de ning the distributions of either of these terms can yield the exact same results.The difference is only in modeling con-venience.I now consider models of the two types.Models are available that induce correlation among options by allowing ij t to be correlated across products rather than indepen-dently distributed,are available (see the generalized extreme-value model,McFadden,1978).One such example is the nested logit model,。
