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统计学中的生存分析与风险比的计算方法统计学中的生存分析是研究人口统计的一种方法，旨在评估个体在特定时间内存活或存活时间的概率。
生存分析常用于医学研究、经济学以及其他社会科学领域。
同时，风险比的计算方法是生存分析的一个重要组成部分。
在本文中，将介绍生存分析的概念、风险比的计算方法以及其在实际应用中的意义。
生存分析是研究人群中事件发生与时间的关系的一种方法。
生存分析的目的是评估个体在一定时间段内存活或存活时间的概率。
该方法广泛应用于医学研究领域，如评估特定疾病患者的存活率、在药物试验中评估治疗效果等。
生存分析中最常见的方法是Kaplan-Meier法。
这种方法通过观察事件发生前存活的个体数，根据事件发生的时间和存活的个体数来估计存活曲线。
这对于评估不同个体在不同时间内存活的概率非常有用。
在进行生存分析时，研究人员还经常关注风险比。
风险比是用来比较两个不同组群中事件发生的可能性。
比如，在研究特定疾病的患者时，我们可能对不同治疗组中患病风险的比较感兴趣。
风险比的计算方法是将两个组的生存曲线进行比较，以评估其差异。
关于风险比的计算方法，最常用的是Cox比例风险模型。
该模型是基于生存数据的半参数模型，可以用于估计不同时期内风险的比例。
Cox比例风险模型的一个重要优点是可以同时考虑多个危险因素，并根据这些危险因素对事件发生的影响进行调整。
除了Cox比例风险模型，还有其他一些计算风险比的方法。
例如，Log-rank检验是一种非参数方法，用于比较两个组之间的生存曲线。
Wilcoxon检验也常用于比较两组之间的生存时间。
风险比的计算方法在实际应用中具有重要意义。
首先，它可以帮助研究人员了解某个因素对事件发生的影响程度。
例如，在临床研究中，可以分析不同治疗方案对患者生存率的影响，从而指导医生进行治疗选择。
其次，风险比的计算方法也可以用于评估各种干预措施的效果。
例如，在公共卫生研究中，研究人员可以比较不同健康政策对疾病发生率的影响，以评估其效果。
基于NAR网络的短生命周期产品需求预测赵小惠;张影【摘要】针对短生命周期产品需求的不确定性和缺乏历史数据,文中利用非线性自拟合的时间序列网络,构建基于NAR神经网络的短生命周期产品需求预测模型.采用某时尚品牌针织开衫的历史销售数据,进行建模仿真并检验模型的模拟能力.研究结果表明,基于NAR网络的短生命周期产品需求预测模型具有较强的非线性动态拟合能力和较高的预测精度.%For the uncertainty of the demand for short life cycle products and lack of historical data,a model for forecasting the demand for short life cycle products is built on the NAR neural network,by using a nonlinear fitting time series network.The simulation of the model is set up according to the historical sales data of a fashion brand knitting cardigan,and then its capability is tested.The results show that the new model has a stronger nonlinear dynamic fitting capability,and higher accuracy.【期刊名称】《西安工业大学学报》【年(卷),期】2017(037)007【总页数】6页(P544-549)【关键词】NAR网络;短生命周期产品;非线性;需求预测【作者】赵小惠;张影【作者单位】西安工程大学机电工程学院,西安710048;西安工程大学机电工程学院,西安710048【正文语种】中文【中图分类】F250科学技术的高速发展，企业之间的激烈竞争以及消费者对个性化的追求，使得产品的生命周期大幅缩短.快时尚品牌ZARA产品每周更新，智能手机、电脑等新产品从推出到退出市场往往只有一年甚至几个月的时间.产品生命周期缩短，给需求预测增加了很大的难度和不确定性.而需求预测的结果通常是生产计划与控制系统的主要信息输入，尤其是主生产作业计划的重要信息输入.因此企业应该加强预测的功能，依据需求预测的结果制定合理的生产计划.目前，对短生命周期产品需求预测的研究主要集中在两个方面：一是在Bass扩散模型的基础上进行相应的扩展.不少学者将需求预测的主要影响因素抽象成数学参数，引入Bass预测模型，如引入季节系数[1-3],消费者偏好[4]、价格影响因子[5]、平均服务影响因子和商品平均重复购买率[6]等；二是尝试采用新的预测模型.文献[7-10]等分别使用简单逻辑模型、龚珀资模型和随时间变化的扩展逻辑模型对短生命周期产品进行需求预测，文献[11]分析比较了龚珀资曲线、逻辑曲线、Bass曲线和时间序列自回归平移模型对手机销售数据的需求预测情况；文献[12-13]提出了一种适合高科技产品扩散的Norton模型，并验证了该模型可行性；文献[14]采用Norton模型预测多代短生命周期产品的市场需求.该模型大多以线性为主，需要准确的定量计算.实际需求中短生命周期产品受到众多主观因素的影响，各参数大小难以用数字准确衡量.短生命周期产品虽然涉及到生产和生活的各个方面，但什么是短生命周期产品，至今仍没有一个准确和统一的定义，文中认为短生命周期产品是时效性强、更新换代快或季节性强的产品.与传统产品相比，短生命周期产品的特征主要体现在六个方面：生命周期较短、提前期较长、库存具有时效性、产品可替代性高、预测初期数据缺乏并且需求不确定性强.而短生命周期产品需求的不确定性受各种因素的影响，如消费者偏好、网络效应、服务水平以及相似产品之间的竞争等.在众多的影响因素中，大多数影响因素都是定性的参数，再加上短生命周期导致预测初期历史数据缺乏，这就给产品的需求预测带来了一定的困难.因此文中针对短生命周期产品需求的不确定性和复杂性，引用非线性自拟合的时间序列网络，建立基于非线性自回归网络(Nonlinear Auto-Regressive,NAR)神经网络的短生命周期产品需求预测模型，采用某时尚品牌针织开衫的历史销售数据进行仿真分析.短生命周期产品其销售变化受到流行趋势、网络效应、消费者偏好以及季节变换等客观因素的影响，这些因素受人的主观行为影响较大，在生命周期的不同阶段对需求预测的影响程度不同，很多需要通过调查进行定性分析，各项因素在构建预测模型时的权重也很难衡量，随机性成为影响销售趋势的主要因素.短生命周期产品的需求预测已成为制约企业发展的瓶颈，因此企业必须研究如何应对产品短暂的生命周期内市场需求的不确定性以及伴随的风险性，在实现快速而有效地满足市场需求的同时，降低自身的运营成本.从而以更加敏捷和柔性的方式来满足市场需求，获取更多的利润.针对短生命周期产品需求预测影响因素的非线性特性，应着眼于产品销售数据本身的特点去挖掘信息，相对久远的销售数据对需求预测的意义不大，应以短期内的销售数据为主，利用需求预测模型去阅读销售数据中的信息，分析出影响因素的个数以及各个影响因素对需求预测的影响程度.非线性自拟合的NAR网络预测模型具有参数持续更新的特点，同时模型只有输出没有输入，不受样本数据的制约，更符合短生命周期产品的特点.短生命周期产品NAR网络需求预测模型的数学表达式为y(t)=f(y(t-1),y(t-2),…,y(t-d))式中:t为当前时期；d为延时变量的个数，即前t-d个时期产品销售情况对当前时期产品需求的影响；y(t-1)为t-1时期产品的销售量；y(t)为预测值，代表当前时期产品的需求量.模型中每一个y(t)的输出，都指向元神经网络层的输入当中，作为下一次输出的调整参数，并且完成对神经网络的调整[15].模型的具体结构如图1所示.图1中左边的y(t)为输入数据，即短生命周期产品已有的销售数据；1∶2为延时变量个数，即t时期的产品需求量受到t-1、t-2时期产品销售情况的影响；w为连接权值，b 表示阀值.1) 短生命周期产品需求预测影响因素的个数隐含层神经元的个数即为影响因素的个数，将需求预测的影响因素抽象成NAR网络预测模型中的参数，参数的确定只需通过设定隐含层神经元的个数来实现.隐含层神经元的个数往往需要根据设计者的经验和多次实验来确定，数目过多或过少都会导致误差增大，影响模型的预测结果.最佳隐含层神经元个数如下：n1=+a式中:n1为隐含层神经元个数；n为初始样本数据；m为输出神经元个数；a为[1,10]之间的常数.神经元之间采用非线性的传递函数为f(x)=这种非线性的传递关系体现了各个影响因素之间的复杂影响关系.若影响产品需求的因素与产品需求之间的关系是完全非线性的，则可以适当增加神经元的个数. 2) 样本数据的大小样本数据的大小通过延时变量的个数来确定.指向元神经网络层的y(t)构成了短生命周期产品需求预测模型的样本数据，延时变量即用来控制有多少个y(t)指向元神经网络层，进而间接确定NAR网络需求预测模型的样本数据.3) 样本数据的分配比例样本数据的大小确定后，开始对需求预测模型进行训练，目的是建立符合短生命周期产品特点的NAR网络预测模型.网络训练的数据分为三类：训练集，即用来训练建立需求预测模型的数据；验证集，即用来验证网络是否符合短生命周期产品的特点；测试集，即用来评估模型预测能力的数据.网络训练过程中根据短生命周期产品的特点进行数据比例的分配和调整.文中采用列文伯特-马奈尔特(Levenberg-Marquardt,LM)训练算法进行神经网络学习，根据误差自相关曲线和误差曲线来判断网络预测模型是否符合短生命周期产品的特点，是否具有较高的预测精度，网络性能采用均方误差(Mean Squared Error，MSE)来评判.MSE指各测量值误差的平方和的平均值的平方根，反映整个整个预测周期内的预测精度，其计算公式为MSE=2式中:n为预测点；yi为真实值；yi′为预测值.对短生命周期产品进行需求预测，在预测的初期只能借助相似产品的历史销售数据，销售量与时间两者的量纲不同，在模型建立的初始，首先对历史数据进行归一化处理，文中采用min-max标准化的方法，对需求预测的历史数据进行线性变换，使结果值映射到[0,1]之间，转换函数如式(5).X*=式中:X*为归一化后的数据；X为原始数据；Xmin为所有历史数据中的最小值；Xmax为所有历史数据中的最大值.对样本数据处理之后，开始构建短生命周期产品NAR网络需求预测模型.首先对相关参数进行设定，然后开始进行网络训练.通过网络训练构建出最符合短生命周期产品特点的NAR网络需求预测模型.根据预测输出与目标输出之间的误差大小关系图以及误差自相关性关系图判断网络是否符合短生命周期产品的特点以及是否达到预期的预测精度.模型建立步骤如下：① 确定短生命周期产品需求预测的样本数据，即通过 Cross-validation方法，确定延时变量个数cv(k).② 设置影响短生命周期产品需求预测的参数，即确定隐含层神的经元个数n.③对数据进行配置，分别设置训练集a1、验证集a2和测试集a3的比例.④ 使用train()函数对网络模型进行训练，学习方法是LM.⑤ 验证网络模型是否符合要求，若不符合要求继续进行第4步的网络训练.⑥ 利用函数closeloop()将网络转化为闭环的网络模型.⑦ 利用第⑥步保存的网络，进行预测，查看预测误差.在短生命周期产品NAR网络预测模型构建的过程中，步骤⑤需要对模型反复训练，寻找出符合短生命周期产品特点和误差要求的网络模型.网络训练结束后若误差过大或者误差自相关性超出了95%的置信区间，则表明NAR网络预测模型预测精度不高，需要对预测模型进行调整.为得到精确的预测值，可以通过对网络训练数据的训练集a1、验证集a2和测试集a3的比例进行调整；调整延时变量个数以及隐含层神经元个数；对网络进行多次训练，调整网络的内部结构改变连接权值w和阀值b的大小三种方法对网络进行调整.采用训练好的短生命周期产品NAR网络需求预测模型进行预测，文中采用递归预测法，对于NAR网络需求预测模型y(tn) = f(y(tn-1),y(tn-2),…,y(tn-d))，当n=1，即对y(tn)预测时，就可以得到第一步预测值y(t1)；当对y(tn+1)预测时，把1步预测y(t1)添加到原样本(y(tn-d),…,y(tn-2),y(tn-1))中组成新的样本(y(tn-d),…,y(tn-2),y(t1))，就可以得到2步预测值y(t2)；然后再对构成的新样本(y(tn-d),…,y(tn-3),y(t1),y(t2))采用短生命周期产品NAR网络需求预测模型得到3步预测值.如此循环，直到得到所需要的n步预测值为止.为了验证预测模型的有效性，文中采用北京地区某时尚品牌服装针织开衫一年内的各周历史销售数据对NAR网络预测模型进行训练，建立符合短生命周期产品的需求预测模型.通过对网络预测模型的多次训练调整，最终确定仿真数据的分配比例为：训练集为75%，验证集15%，测试集15%.隐含层神经元的个数为35，延时变量个数为1∶3.NAR网络需求预测模型中，一般通过误差自相关图以及误差图判断模型预测能力的优劣.企业对短生命周期产品的实际需求预测中，误差影响制造商的生产和零售商的销售，直接影响企业的经济利益.因此，采用误差自相关图以及误差图判断网络模型的预测能力，具有较好的现实意义.1) 误差自相关图误差自相关性分析就是检测时间序列各个预测点误差的相关程度，可根据误差相关程度的大小来对比模型预测性能的优劣.若一个模型的预测能力良好，误差的自相关性在时间间隔为0时应该最大，其他情况下均应在95%的置信区间内，最好的结果是其余情况下误差均为0.但是网络预测模型不可能达到绝对的零误差.如图2所示即为短生命周期产品NAR网络需求预测模型的误差自相关图.分析可知误差在合理的范围内，并且误差值都相对较小.可见NAR网络预测模型的整体预测值不会因为一个预测点的误差较大而使整体产生较大的偏差.2) 误差图误差，即预测输出与目标输出之间的差值.预测输出与目标输出之间的差值越小，表明NAR网络预测模型的预测精度越高.图3为短生命周期产品需求预测模型的误差图.由图3可知，只有少数个别的时间点出现了误差，其余时间点误差均为0.从产品的整个生命周期来看，网络的预测精度较高，预测效果较好.为了验证模型的预测效果，采用同一地区同一针织开衫2007年一年内各周的销售数据对针织开衫NAR网络需求预测模型进行验证.验证结果显示，网络误差在±2之间，即一周内针织开衫的预测误差2件.网络误差的自相关性均在95%的置信区间内，MSE为0.000 38.由此可以看出NAR网络预测模型对短生命周期产品的需求预测具有很好的适应性以及较高的预测精度.文中采用循环预测的方法对2008年1月的针织开衫各周销售量进行预测.循环预测的网络结构如图4所示.由于在需求预测的初期缺乏销售数据，因此只能借助相似产品的历史销售数据.首先，将2007年12月四周的历史销售数据带入针织开衫NAR网络需求预测模型，预测出2008年1月第一周的需求量；然后将1月第一周的预测需求量以及12月份后三周的销售量数据带入NAR网络需求预测模型预测出1月份第二周的需求量；如此循环，预测出第三周、第四周的针织开衫的需求量.各周次NAR网络模型预测评价指标预测结果的均方误差分别为0.003 8，0.004 5，0.011 35，0.011 48.短生命周期产品中的服装产品，需求的不确定性更强，相邻年份的同一季节服装需求量就可能相差很大.但是由于NAR网络需求预测模型样本数据以及影响参数持续更新的特点，在仿真过程中，网络内部对数据进行一系列的非线性处理，通过分析数据计算参数的大小.因此各个时期的预测误差不会出现较大的偏差.短生命周期产品的需求预测受到众多客观因素的影响，客观因素的不确定性以及预测初期历史数据缺乏，造成了短生命周期产品需求预测的不确定性和复杂性.同时影响因素的非线性导致传统的预测模型无法准确预测短生命周期产品的需求.NAR网络预测模型具有较好的非线性映射能力和自适应能力，不受样本数据量的制约，文中利用非线性自拟合的时间序列网络，构建了基于NAR神经网络的短生命周期产品需求预测模型，同时借助算例说明了该模型具有较高的预测精度，并验证了预测模型的有效性.【相关文献】[1] 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统计学中的生存分析技术生存分析是统计学中一个重要的技术，用于研究个体或群体在特定条件下的生存时间。
它可以帮助我们了解各种事件（如死亡、失业、疾病等）发生的概率和时间。
生存分析技术有多种方法，其中最常用的是卡普兰-迈尔曲线和考克斯比例风险模型。
1. 卡普兰-迈尔曲线卡普兰-迈尔曲线是一种常用的生存分析方法，它可以帮助我们估计在不同时间点上存活的概率。
该方法可以应用于各种涉及生存时间的研究，比如医学研究、流行病学研究和工程研究等。
卡普兰-迈尔曲线通过对事件发生时间进行排序，然后根据事件发生的时间和状态（生存与否）来计算每个时间点的生存概率。
通过绘制曲线，我们可以观察到在不同时间点上生存概率的变化情况。
2. 考克斯比例风险模型考克斯比例风险模型是另一种经常用于生存分析的方法。
它可以帮助我们分析个体或群体在不同条件下面临事件发生的风险。
考克斯比例风险模型基于风险比例的概念，即相对于某个基准组群，其他组群的风险大小。
它假定个体的风险与其特征和其他因素相关，通过对不同因素进行建模，我们可以估计每个因素对生存时间的影响。
3. 应用案例生存分析技术在许多领域都有广泛的应用。
以下是一些常见的案例：3.1 医学研究生存分析技术在医学研究中具有重要意义。
例如，研究某种疾病的患者生存时间可以帮助医生了解疾病的进展情况和预后。
通过对疾病特征和治疗方式等因素进行分析，可以为患者提供更好的治疗方案。
3.2 肿瘤学研究肿瘤学研究是生存分析技术的一个重要应用领域。
通过分析患者的生存时间和疾病特征，可以帮助医生评估肿瘤的危险程度，制定更合理的治疗方案。
3.3 经济学研究生存分析技术在经济学研究中也有广泛的应用。
例如，研究失业人群的存活时间可以帮助政府了解劳动力市场的状况，并采取相应的政策措施。
4. 总结生存分析技术是统计学中的一个重要工具，可以帮助我们分析个体或群体在不同条件下的生存时间。
卡普兰-迈尔曲线和考克斯比例风险模型是常用的分析方法，它们在医学研究、流行病学研究和经济学研究等领域有广泛的应用。
Filing Information: July 2008, IDC #CN221105Q, Volume: 1, Tab: MarketsM A R K E T A N A L Y S I S C h i n a I T S e r v i c e s 2008–2012 F o r e c a s t a n d A n a l y s i s Grace Han Ting Yang Vivian Yu Gloria Li I D C O P I N I O N China's IT services market is facing both domestic demand and offshore opportunity. With global sourcing becoming a strategic decision of companies to lower costs and enhance core competencies, the country boundary among services is blurring. To better capture this global sourcing opportunity, IDC strongly suggests leveraging China's comparative advantages and using the economies of scope by developing both domestic and offshore IT services industries collaboratively. ! 2007 was still a bull year for IT services players in China, especially the leading services providers. With the market gradually consolidating, the top 10 services providers' gained share from 17.0% in 2006 to 19.7% in 2007. ! The market size also grew very fast, from US$6239.8 million in 2006 to US$7699.1 million in 2007, with a 23.4% year-on-year growth. This is 1.1% higher than IDC's previous forecast. Looking forward, China's IT services market will still be in the double-digit growth stage for the next five years, with a 2007–2012 compound annual growth rate (CAGR) of 16.2%, although the growth rate will be slightly lower than that in the past two years. ! For IT services, as observed, a large amount of competition comes from the clients' internal IT departments. Because of this, it is very important to understand users' adoption rates of third-party services providers, reasons for insourcing, and vendor evaluation criteria. ! For outsourcing services, the dilemma in China is that labor costs are low, so the cost effectiveness of outsourcing, especially by global vendors, is not apparent. Clients' IT environments are currently very complicated and non-transparent; it is hard to realize vendors' technical and management expertise in such situation. Consulting services should be provided to help improve the IT operation level first, and then try selective outsourcing to build up trust before continuing to outsource more. Managed services are also a very smart way to solve the control preference of clients in China. ! In the long run, utility services will be well received by users due to their significant cost effectiveness and high expertise, which is difficult to maintain in an internal IT department.R o o m 611,Bei j i n g T ime sSqu a re88 W e stC h a n g 'a n A ven u e B ei j i n g 100031 P eo p l e 'sR e p u b l i co f C h i n a P .86.10.8391.3610T A B L E O F C O N T E N T SPIn This Stud y 1 Methodology (1)Situat ion Overview 1Global Sourcing Impact (1)User Demand and Buying Behavior (2)IT Services Overview (6)IT Services by Submarket (8)IT Services by Industry (14)IT Services by Region (15)Competitive Landscape (16)Future Ou tlook17Forecast and Assumptions (17)Future Trends (26)China IT Services Road Map (26)Market Context (29)Essential Gu idance30Advice to Technical Product Services Providers (30)Advice to Consulting Firms and Systems Integrators (31)Advice to Outsourcing Players (32)Learn Mo re32Related Research (32)Definitions (32)IT Services Foundation Market Definitions (32)Regional Markets (35)IDC #CN221105Q ©2008L I S T O F T A B L E SP1 Top 10 China IT Services Providers, 2007 (17)2 China IT Services Spending by Foundation Market, 2007–2012 (US$M) (18)3 Key Forecast Assumptions for the China IT Service Market, 2008–2012 (19)4 China IT Services Spending, 2005–2012: Comparison of July 2008 and September 2007Forecasts (US$M) (29)5 China Regional Market Definitions, 2007 (35)©2008 IDC #CN221105QL I S T O F F I G U R E SP1 Economic Analysis of Global Sourcing (2)2 Competition Models of Products and Services (3)3 Use of a Third Party or an Outside Vendor for Managed Services (4)4 Reasons for Maintaining In-House IT Services Management (5)5 Selection Criteria for IT Services Providers (6)6 China IT Services Life Cycle (7)7 China and United States Different Outsourcing Stages (8)8 China IT Services Spending and Year-on-Year Growth Rate by Foundation Market,2007–2012 (9)9 China Consulting and Systems Integration Growth Rate and Share, 2007 (10)10 China Outsourcing Growth Rate and Share, 2007 (12)11 China Technology Product Services Growth Rate and Share, 2007 (13)12 China IT Services Market Spending by Industry, 2007 (15)13 China IT Services Market Spending by Geography, 2007 (16)14 China IT Services Road Map (27)15 China IT Services Spending, 2005–2012: Comparison of July 2008 and September 2007Forecasts (30)IDC #CN221105Q ©2008I N T H I S S T U D YThis IDC study provides an overview of the status of the China IT services marketand a forecast for the next five years. The study also includes a demand-sideanalysis, a competitive landscape with top vendors' rankings, as well as a segmentanalysis. IDC also provides recommendations for services providers in each ITservices segment.M e t h o d o l o g yThis study is part of the continuous effort by IDC to research the China IT servicesmarket. IDC China services analysts get secondary information from, but are notlimited to, the following: the Internet, trade publications, previous IDC research, andIDC's proprietary database. Both primary and secondary research approaches areused in conjunction with each other to validate and cross-check information, asfollows:! Interviews with IT services providers. IDC China Services analysts interview all significant participants in the IT services market to determine the marketrevenue and other relevant information. Most interviews were conducted inperson, although other data-collection methods, such as telephone or faxinterviews, were applied when needed.! Provider briefings, press releases, and other publicly available information.IDC services analysts meet with a large number of service providers (SPs)semiannually. These briefings provide an opportunity to review current and futureservice offering strategies, revenue, customer bases, target markets, and otherkey market information.Ultimately, the data presented herein represents IDC's best estimates based on theabove data sources, reported and observed activity by providers, and furthermodeling of data that we believe to be true to fill in any information gaps.Note: All numbers in this study may not be exact due to rounding.S I T U A T I O N O V E R V I E WG l o b a l S o u r c i n g I m p a c tChina's IT services market is facing both domestic demand and offshore opportunity.With global sourcing becoming a strategic decision of companies to lower costsand enhance core competencies, the country boundary among services is blurring.Figure 1 illustrates the economic analysis and the impacts of global sourcing.For sourcing countries (e.g. the United States), clients there can enjoy lower pricesdue to the increase of supply from offshore vendors. The equilibrium point will movefrom point E to point E', where clients will have a greater surplus, while U.S. domesticvendors' surplus in the sourcing country will decrease. Thus, United States–basedglobal vendors like IBM and HP keep on building global delivery centers to solve thechallenge.©2008 IDC #CN221105Q 1O u t sou r cin g M a rke tAs many organizations are completing the first round of IT infrastructure implementation, they are shifting their focus on how to improve business efficiency and realize reliable business continuity (BC). After years of market cultivation and informing clients about the benefits of IT outsourcing services, organizations are more welcoming of professional services from outsourcing vendors and of buying into a model of business value improvement rather than just pure cost reduction through outsourcing.The China outsourcing market reached US$1,098.2 million in 2007, with a year-on-year growth of 36.2%. As for the current outsourcing market, we forecast it will evolve both in service expansion and project complexity. Organizations that have adopted outsourcing models are usually taking leading positions among the competition and are pioneering technology innovation. They are ready to entrust more projects with professional service vendors if they truly benefit from this model. The incremental market for outsourcing services will continue to boom on the similar track of the current existing market, and will generate more business from the China SME market. Requirements for outsourcing in the SME market will take more time to improve to maturity, but the huge customer base provides large business potential for this market. Local channels that have a wide social network and deep understanding of local potential customers will stand more chances to gain business from the local SME market. These traits are considered an important alliance necessary to leading IT outsourcing service vendors wanting deep market penetration.Big organizations that have a clear outsourcing strategy and streamlined business processes are capable of purchasing IS outsourcing (ISO) services to realize economies of scale and to transfer more management responsibility to vendors. Most organizations in the SME market are inclined to start outsourcing business from noncore or low-level transactional projects with vendors that match them in size and price. In the outsourcing market, we have observed that both global and local IT outsourcing vendors are struggling to find the right place that suits their scale and capability. Leading vendors target organizations demanding strategic and highly integrated services, while other small vendors improve themselves by collaborating with local small businesses. Interestingly, in taking advantage of China's rapid economic growth, many small businesses in China are experiencing their own dramatic growth and are willing to extend cooperation to existing vendors rather than launch new vendor selection campaigns, given the vendors fulfill their business requirement. This customer preference helps local outsourcing vendors expand their service coverage, deepen their industry knowledge, and therefore improve their competitive edge in the outsourcing field.Many services providers have launched series of services, such as IBM, Bluex, and Lenovo-Sunny services. These service offerings make it easier for customers to choose what they should buy when they encounter problems.With an increased reliance on software and hardware for mission-critical operational environments, enterprises prefer to contact support providers whenever a problem occurs — regardless of when or where it happens. Therefore, many support providers continue to launch advanced support services to better fulfill their customers' requirements.Increasingly, enterprises are looking for a single point of contact for their enterprise software and hardware support services. To meet the customers' needs, more and more SPs are carrying on multivendor support services to enrich their multibrand maintenance technical ability.To ensure peak performance and reliability of the entire IT system, an enterprise must implement a comprehensive strategy to support its IT environment. The product manufacturers are continuing innovation on the form of support services. Along with the fierce market competition, they have gradually been breaking away from being a single product support provider, and are tending to change into professional and personal value-added service (VAS) providers.In addition, product manufacturers try to penetrate tier 4 or 5 cities and expand their footprints. They are scrambling for service channels and entrusting them with more product-related services to penetrate local industry-centric markets and fulfill customers' needs.Beyond traditional customer training, vendors are making more efforts in channel education as channels gain value and become more important to vendors.IT Services by IndustryThe industry segmentation of the 2007 China IT services market was similar to that in 2006; the top 4 industries contributed 80% to the total market revenue. The top 4 industries include finance, communications and media, manufacturing, and government.In most of the industries, the growth engine came from the SME sector. The SME segment is unique because of its approach to purchasing IT solutions, particularly in terms of the emphasis on price. As such, vendors need to increase the number of channel partners and provide solutions/services to help drive growth in this market. There are strong growth opportunities in the SME market, including smaller cities. However, the uniqueness of the SME market coming from price sensitivity, limited IT demand, and flexible IT requirements still poses challenges for IT services providers.Figure 12 shows various industry shares in overall IT services spending in 2007.Accenture maintained its high and healthy growth in 2007. Continuing the strategy ofproviding business consulting services for resources, power, and telecom industriessharpened its business focus and made its market position clear. Accenture alsoprovides IT outsourcing services after implementing SI services for industry clients.AsiaInfo is a newcomer to the top 10 list. AsiaInfo mainly provides CRM, networkmanagement solutions, CAD, consulting, and SI services to the telecom industry.It enjoyed growth of 27.6% in 2007 over 2006. China's telecom industry marketis inclined to change from being demand driven to being layout driven; thisreorganization and realignment of the telecom industry along with the emergence of3G will bring more opportunities.Table 1 shows the revenue and market share of the top 10 IT SPs in China in 2007.T A B L E1T o p10C h i n a I T S e r v i c e s P r o v i d e r s,2007Ranking Vendor Revenue (US$M) Market Share (%)Services 533.1 6.1 Global1 IBM2 HP 314.9 3.6China 221.9 2.63 Digital4 Huawei 179.0 2.15 Accenture 105.0 1.2Technology 82.9 1.0 Dongli6 CE7 Neusoft 78.2 0.98 Dell 67.9 0.89 CS&S 66.3 0.810 AsiaInfo 60.9 0.7 Others 6,970.9 80.3 Total 8,681.0 100.0Note: The total market size in this table includes both primary and secondary markets. Therefore, the total market size islarger than the 2007 services market size. The primary market represents the IT services spending from the client and thesecondary market represents the IT services revenue from the vendor's subcontracting.Source: IDC, 2008F U T U R E O U T L O O KF o r e c a s t a n d A s s u m p t i o n sTable 2 shows the expected expenditures in the various foundations within the overallIT services market in China from 2007 to 2012.T A B L E 2C h i n a I T S e r v i c e s S p e n d i n g b y F o u n d a t i o n M a r k e t , 2007–2012 (U S $M )2007 2008 2009 2010 2011 2012 2007–2012CAGR (%)C&SICAD 1,110.3 1,307.4 1,491.8 1,690.6 1,913.4 2,178.1 14.4 IT consulting 311.7 373.6 440.3 535.5 650.9 795.8 20.6 SI 1,814.9 2,146.6 2,498.4 2,948.9 3,457.0 4,054.6 17.4 C&SI total 3,236.9 3,827.6 4,430.5 5,174.9 6,021.3 7,028.5 16.8 C&SI growth 25.9% 18.2% 15.8% 16.8% 16.4% 16.7% Outsourcing Application management 140.0 193.3 262.1 346.0 431.9 541.8 31.1 Desktop management 285.6 371.4 482.0 612.0 762.3 940.4 26.9 Hosted application management 100.1 128.9 157.1 199.0 249.4 307.1 25.1 Hosted infrastructure services 119.0 150.7 185.4 220.7 262.7 309.9 21.1 IS outsourcing 214.0 261.7 319.3 385.5 454.0 522.4 19.5 Network management 239.5 319.6 412.1 525.4 666.4 806.6 27.5 Outsourcing total1,098.2 1,425.7 1,818.0 2,288.6 2,826.6 3,428.2 25.6 Outsourcing growth (%) 36.2 29.8 27.5 25.9 23.5 21.3 TPSHardware deployment & support 1,390.0 1,556.5 1,713.8 1,900.7 2,123.7 2,350.9 11.1IT education & training 481.8 529.6 587.0 652.0 723.0 788.8 10.4 NCIS 842.9 930.2 1,007.5 1,084.8 1,192.0 1,298.3 9.0 Software deployment & support 649.4 784.6 922.9 1,071.4 1,240.6 1,443.417.3TPS total 3,364.0 3,800.8 4,231.2 4,708.8 5,279.3 5,881.3 11.8 TPS growth (%) 17.5 13.0 11.3 11.3 12.1 11.4 Grand total 7,699.1 9,054.1 10,479.812,172.414,127.216,338.016.2Grand total growth rate (%)23.417.615.716.216.115.6Note: See table 3 for key forecast assumptions.Source: IDC, 2008Table 3 is a look at the key assumptions for the China IT services market.K e y F o r e c a s t A s s u m p t i o n s f o r t h e C h i n a I T S e r v i c e M a r k e t,2008–2012Market Force IDC Assumption Impact Accelerator/Inhibitor/NeutralCertainty ofAssumptionMacroeconomicsGross domestic product (GDP) growth China maintained high GDPgrowth of 11.4% in 2007. Thisgrowth is expected to slowdown slightly in 2008,decreasing to 9.6%. Althoughgrowth in 2008 was adjustedto lower than the previousestimates due to theslowdown in the globaleconomy, it will be backed bystrong domestic demand.Domestic consumption willremain firm, with acceleratinggovernment spending anddemand in rural areas playingsignificant roles.Moderate. IDC assumes thatmore effective measures takenby the government will helpreduce the risk of economicoverheating and thus have nomajor impact on most ITmarkets. A strong and healthyeconomy will translate intoincreased overall IT spendingaccompanied by improvedbusiness sentiments andconfidence as well asexpanded domestic market.↔###$$U.S. recession The global economic outlookis increasingly grim as effectsof the housing meltdowncontinue to spread and creditconditions remain difficult.Contrary to previous IDC'sassumptions that the UnitedStates might be able to pullitself back from falling into arecession, the possibility of arecession is increasinglypossible. As the U.S.economy continues tocontract, it is likely that it willslide into a mild recession,and will stagnate throughmuch in 2009. Low. While some export-intensive countries mayexperience a squeeze, there isenough domestic demandacross most countries in theregion to sustain IDC's ongoingIT spending forecasts. Anynegative effects from the UnitedStates might even be a goodthing in helping to ease somepotentially overheatingcountries in the region.↓###$$Interest rates Up until December 25, 2007,China's central bank hadincreased the deposit rate by5.5% after 10 adjustmentsand increased the interest rateby 1.62%, intervening sixtimes in total. Thesemeasures were taken to keepconsumer prices from risingtoo fast and to turn around thesituation of negative interestrates. In 2008, the interestrate will keep rising under thepressure of inflation. Moderate. The continualincreasing interest rates willmake bank loans moreexpensive and thus makecompanies cautious inexpanding IT investments.↓##$$$K e y F o r e c a s t A s s u m p t i o n s f o r t h e C h i n a I T S e r v i c e M a r k e t,2008–2012Market Force IDC Assumption Impact Accelerator/Inhibitor/NeutralCertainty ofAssumptionInflation The pork crisis largely droveup China's consumer priceindex (CPI) in 2007 and wasconsidered a signal of generalinflation. The CPI recorded itshighest levels in 11 years,reaching 6.9%, bringing theaverage annual CPI to 4.8%.The China government hasmade the task of avoidingoverall inflation a high priorityin 2008. Low. Expectations of highinflation are becoming moreentrenched among the public,and demand-driven inflationarypressures will remain relativelystrong in 2008. Nonetheless,the average inflation isexpected to fall slightly after thewidely celebrated Lunar NewYear, as demand for porkeases. Inflation will not impactIT spending patterns to a largeextent.↓###$$China's yuan revaluation Revaluations of the yuan mayoccur again in the future,although they would mostlikely occur very gradually, ifat all.Low. Even if anotherrevaluation occurs, there will beno major disruptions to theeconomy as a result (both forChina itself as well as othercountries in the region thattrade heavily with China).↓###$$Urbanization The government has devoteditself to facilitatingurbanization in the next fiveyears. Three initiatives includeincreasing the urbanproportion in the totalpopulation, increasing thenumber of cities, and reducingthe gap between urban andrural areas by improving theeconomy, culture, and livingenvironment in thecountryside. High. The standard of living inthe countryside will beimproved, and the consumptionof and investment in IT willincrease, especially in SouthChina and East China. Closingthe gap between the urban andrural areas together will alsohelp reinforce social stability.↑####$Foreign direct investment (FDI) The increasing FDI in China isstrongly fueling economicgrowth. This trend is expectedto continue for the next 2–3years.High. Increasing FDI isbolstering stable andsustainable infrastructureinvestments as well as rapidgrowth in spending in the ITservice market. Joint venturesand foreign-owned enterprises(FOEs) are more inclined toadopt IT services comparedwith state-owned enterprises(SOEs) and privately ownedenterprises (POEs).↑###$$K e y F o r e c a s t A s s u m p t i o n s f o r t h e C h i n a I T S e r v i c e M a r k e t,2008–2012Market Force IDC Assumption Impact Accelerator/Inhibitor/NeutralCertainty ofAssumptionMarket ecosystemMinistry of Information Industry (MII) 11th Five-Year Plan The MII has set its 2006–2010five year IT plan. The strategyof "information technologygives an impetus toindustrialization andindustrialization promotesinformation technology " putsthe IT industry as a toppriority, and technology will beencouraged to be used widelyin all economic and socialfields to promote economicstructure adjustment andindustrial development.Low. This plan has littlesurprises but imposes anoptimistic atmosphere for the ITservices market.↑####$IT for SMEs The SME segment is uniquebecause of its approach topurchasing IT solutions,particularly in terms of theemphasis on price. As such,vendors need to increase thenumber of channel partnersand provide solutions/servicesto help drive growth in thissegment. Moderate. There are stronggrowth opportunities in theSME market, including smallcities. However, the uniquenessof the SME market in pricesensitivity, limited IT demand,and flexible IT requirements stillpose challenges for IT serviceproviders.↑####$2008 Summer Olympics The 2008 Summer Olympicswill be held in China in August2008. This will not only serveas a healthy economicstimulus but will also requireservice providers to preparefor hosting and relevant SIprojects.Moderate. The games will fuelservice industries such astourism, hotel and restaurant,B2C, and online trading.As such, service enterpriseswill invest more in ecommerceor SaaS to enable moreefficient and effective accessfor consumers.↑###$$Technology/Service developmentsGlobal sourcing Both domestic and pure-playoffshore providers areincreasing their globalsourcing sophistication inChina, allowing forhigher-quality levels at lowerblended rates. Additionally,these benefits andexperiences are being passedonto local services markets asthey increase. Moderate. The maturation ofoffshore offerings will increasethe overall market opportunityby allowing existing customersto expand the scope of theircontracts and by allowing newcustomers to utilize servicesthat were previously tooexpensive; the price pressureswill negate much (but not all) ofthat effect on the overallservices markets.↔###$$K e y F o r e c a s t A s s u m p t i o n s f o r t h e C h i n a I T S e r v i c e M a r k e t,2008–2012Market Force IDC Assumption Impact Accelerator/Inhibitor/NeutralCertainty ofAssumptionNevertheless, the net impact of increased market opportunity will somewhat outweigh decreased prices.On-demand/Utility computing Technologies such asvirtualization and gridcomputing will enable thedelivery of real "pay by thedrink" computing by bothtraditional outsourcers andnew entrants. Thisdevelopment will begin toaffect the traditionaloutsourcing market as well asother infrastructure-intensiveservices markets.Moderate. The impact will below for the near term (twoyears) as adoption takes hold.These technologies will affectprofitability as opposed torevenue in the near term.Competition and lower costswill stimulate demand andaccelerate migration frominternal to external spending.This service model will bepopular among SMEs since ithelps them realizeinformatization with limited ITbudgets.↑###$$Industry restructuring One of current revolutionaryfocus areas for organizationsis optimizing industry structure— weakening high resource-costing, labor-intensive, andlow added-value industrieswhile encouraging efficient,high-tech, and highadded-value industries.Moderate. The transformationfrom external to internaleconomic growth will giveconfidence to high-techindustries, led by theinformation industry, to reachstrategic heights as the driverof structural change andgrowth.↑###$$Security and BC services Security is in demand bysectors such as ebusiness,government, and legal inChina. Both local andmultinational vendors are thusaddressing security and BC.Moderate. This shouldstimulate both hardware andtotal solution demand.Purchases of consulting andimplementation andoutsourcing with high security,BC, and disaster recovery (DR)will increase, including interestfrom the egovernment, army,and police sectors.↑###$$K e y F o r e c a s t A s s u m p t i o n s f o r t h e C h i n a I T S e r v i c e M a r k e t,2008–2012Market Force IDC Assumption Impact Accelerator/Inhibitor/NeutralCertainty ofAssumptionDynamic IT IDC has identified the nextstyle of computing — dynamicIT for dynamic enterprises —as one that dramaticallyincreases the effectiveness ofIT. Dynamic IT will supportboth business strategy and IToperational efficiency through12 key technologies. Withindynamic IT are a number ofimportant subtrends —virtualization in thedatacenter, data federation,and composite and rule-basedapplication. Transition todynamic IT will be slow andlabored but will proceednonetheless. High. Dynamic IT, by addingcoherence to the enterpriseusage of IT, will spur the ITservices market. However,confusing choices forenterprises and funding hurdlesfor a new infrastructure willbalance this impetus to marketgrowth. ↑###$$Software The software market will keepdouble-digit growth in the nextfive years, and many hotsolutions like SOA and ITservice management (ITSM)will increase the convergencebetween software andservices. Moderate. Software-relatedservices, such as softwaredeployment and support,software implementation, andconsulting services, willincrease.↑###$$SOA To implement services-oriented, architecture-typeprojects and increasebusiness agility, clients need afair amount of consulting andimplementation services tobuild an architecture based onits business process and tointegrate it with legacysystems. High. SOA movement will driveservices market growth rapidly.↑###$$Market environment The increased adoption of thehosting application model andthe number of enterprisedatacenters, as well as thecontinual drop in internetcosts, are providing a positiveenvironment for outsourcingservice providers to developtheir business. High. A favorable marketenvironment will accelerategrowth in IT services market.↑####$。
文章编号:100725429(2007)0520027205收稿日期:2006210225; 修回日期:2006212225基金项目:国家自然科学基金资助项目(70472059)作者简介:徐贤浩(19642),男,湖北武汉人,博士,副教授,主要研究方向为生产运作管理、物流与供应链管理、现代项目管理理论与方法。
改进BASS 模型应用于短生命周期产品需求预测徐贤浩,宋奇志(华中科技大学管理学院,湖北武汉430074) 摘要:总结了目前国内外文献对短生命周期产品需求预测的研究,分析了短生命周期产品需求相关的特点。
介绍了BASS 模型及其发展,通过可行性分析,将BASS 模型应用于短生命周期产品预测。
利用类似产品补充预测所需信息,并对模型进行了季节性修正。
算例预测结果表明,改进后的BASS 模型应用于短生命周期产品的需求预测在MAD 、RMSE 、MA PE 等各项误差指标方面都优于其他方法。
关键词:短生命周期产品;预测;需求;BASS 模型中图分类号:F272.1 文献标识码:AForecasting for Products with Short LifeCycle B ased on Improved BASS ModelXU Xian 2hao ,SON G Qi 2zhi(School of Management ,Huazhong University of Science and technology ,Wuhan 430074,China ) Abstract :The forecasting st udies for short life cycle p roduct s were summarized in t his pa 2per.The of short life cycle product s were analyzed.BASS model and it s develop 2ment were int roduced.After feasibility analysis ,BASS model was applied to forecast t he demand of short life cycle p roduct s.The forecasting information was complemented wit h t he similar prod 2uct data and t he model was revised wit h seasonal factor.The numerical illust ration proved t hat t he revised BASS model could generate good forecast for p roduct s wit h short life cycle.The fore 2casting error of MAD ,RMSE and MA PE were better t han ot her met hods.K ey w ords :short life cycle p roduct ;forecast ;demand ;BASS model1 引言随着科学技术发展的速度加快,产品生命周期越来越短。
生存分析之不满足风险比例假定的竞争风险模型：STATA还是R，总有一款适合你！笔者在<<非比例风险的Cox回归模型_分层分析法>>中用到一个例子：示例：从TCGA（The Cancer Genome Atlas, 癌症基因组图谱，/）下载的多发性骨髓瘤CoMMpass研究中的临床资料（2021年9月），数据经过了清理。
变量包括id、age（年龄）、gender（性别，0=female；1=male）；race（种族：0=white；1=others）、FamHist（家族癌症史：0=No；1=Yes）、stage（病理学分期：1=I 期；2=II期；3=III期）、Trt（治疗方案，0=药物联合治疗，1=制剂+干细胞移植），status（状态：0=alive；1=dead）、cause（死亡原因：0=Alive；1=Not Cancer Related；2=Cancer Related）；time（确诊后生存时间，days）。
治疗多发性骨髓瘤时在药物治疗中加入干细胞移植有助于降低患者的癌症死亡率？疾病介绍：中国多发性骨髓瘤诊治指南（2022年修订），/zLN0Uqi9，密码：Memocl严格来说除了以全因死亡为研究结局，以死因、复发等为结局的研究都广泛存在着竞争风险。
非癌症相关死亡的发生的时候，癌症死亡就不可能出现了，也就是说癌症相关死亡和非癌症相关死亡互为竞争事件。
<<非比例风险的Cox回归模型_分层分析法>>中没有使用全因死亡作为死亡事件只是为了示例非比例风险的Cox回归模型的分层分析法，因为如果以全因死亡作为研究结局，stage等变量都满足风险比例假定，就不需要进行分层分析了。
生存分析的竞争风险模型笔者前面也做过一次长篇笔记：《R笔记：生存分析之竞争风险模型[概念与实操]》。
竞争风险模型有两种分析方法：（1）特定原因风险模型，（2）子分布风险模型。
晚期恶性肿瘤患者生存期影响因素的相关性分析顾筱莉;成文武【摘要】Background and purpose:How to predict the survival length for terminally cancer patients is very important, it will help families and physicians to make decisions. This study aimed to reveal the factors related to the survival time of terminally ill cancer patients who received palliative care in our hospital. Methods:The clinical data of 271 dead patients treated in the Department of Palliative Care, Fudan University Shanghai Cancer Center from Mar. 2007 to Mar. 2012 were analyzed. The Kaplan-Meier method and the log-rank test were used to determine the corresponding factors with survival. Cox regression model was used to examine the independent prognostic factors. Different survival length of groups divided by different prognostic indexes was compared by log-rank test. Results:Seven factors were found to be related with the survival according to univariate analysis. The related factors were Karnofsky performance score (P<0.001), dyspnea (P=0.037), delirium (P=0.015), high white blood cell count (P=0.012), low lymphocyte percentage (P=0.030), high lactate dehydrogenase (P<0.001) and low serum albumin (P=0.001). The multivariate analysis selected four independent factors:Karnofsky performance score<30, high lactate dehydrogenase, low serum albumin and delirium.Conclusion:The study shows the clinical survival prognostics with Chinese characteristics. The combination of the seven factors may be useful but more studies in this area deserve further investigated.%背景与目的：晚期恶性肿瘤的预后判断在肿瘤治疗领域中非常重要，预后判断准确可以帮助临床医师选择相关的治疗。
