英语翻译路桥081高彦召
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7.8 Hypothesis Testing 7.8 假设测试路桥081 高彦召20082201301 Very often traffic engineers must make a decision based on sample information. For example, is a traffic control effective or not? To test this, we formulate a hypothesis,H a, called the null hypothesis and then try to disprove it.The null hypothesis is formulated so that there is no difference or no change, and then the opposite hypothesisis called the alternative hypothesis, H j •很久以前，交通工程师们就必须根据样本的信息做出决定。
例如：交通控制是否起作用？为了检验它，我们构想出一个假设HO。
叫做失效的假设，然后试着推翻它。
这个失效的假设是这样设想的：他没有不同和变化，所以他的反面的假设叫做可选择的假设H1When testing a hypothesis, it is possible to make two types of errors: (1) We could reject a hypothesis that should be accepted (e.g., sayan effective control is not effective). This is called a Type I error. The probability of making a Type I error is given the variable name,0'.(2) We could accept a false hypothesis (e.g., sayan ineffective control is effective). This is called a Type II error. A Type II error is given the variable name f3."当测试一个假说，它有可能有两种类型的错误：（1）我们可以拒绝一个本应该被接受的假设（例如，说有效的控制是无效的）。
这就是所谓的I型错误。
用变量名a表示第一种事件发生的可能性（2）我们可以成立一个虚假的假设（例如，无效的控制是有效的）。
这就是所谓的II型\错误用变量名b表示第二个事件的可能性。
Consider this example: An auto inspection program is going to be applied to 100,000 vehicles, of which 10,000 are "unsafe" and the rest are "safe." Of course, we do not know which cars are safe and which are unsafe.."考虑下面的例子：一个自动检查计划将被应用到100,000辆车，其中10000是“不安全”，其余的是“安全”。
当然，我们不知道哪辆车是安全的，哪些是不安全的。
"We have a test procedure, but it is not perfect, due to the mechanic and test equipment used. We know that 15% of the unsafe vehicles are determined to be safe, and 5% of the safe vehicles are determined to be unsafe,as seen in Figure 7.6."我们有一个测试程序，但它并非十全十美，由于在机械和测试设备使用。
我们知道，15％是不安全的车辆确定为安全，和5％的车辆安全确定为不安全的，就像在图7.6。
"We would define: H o: The vehicle being tested is "safe," and Hi: the vehicle being tested is "unsafe." The Type I error, rejecting a true null hypothesis (false negative), is labeling a safe vehicle as "unsafe." The probability of this is called the level of significance, a, and in this case a = 0.05. The Type II error, failing to reject a false null hypothesis (false positive), is labeling an unsafe vehicle as "safe." The probability of this, b is 0.15. In general, for a given test procedure, one can reduce Type I error only by living with a higher Type II error, or vice versa."我们将定义：H0：被测试的车辆是“安全”和Hi：被测试的车辆是“不安全”。
第一类错误，拒绝真正的无效假设（错误的观点），作为安全汽车“不安全”的标签。
A 作为这种水平的概率，在这种情况下a= 0.05。
第二类错误，不拒绝无效假设（错误的态度），是标示为不安全的车辆为“安全”。
这个概率，{b=0.15。
一般来说，给定的测试程序，一个人可以减少误差只有I型\生活有较高的第二类错误，反之亦然。
"7.8.1 Before-and-After Tests with Two Distinct Choices在得到两个不同截然不同的结果前后In a number of situations, there are two clear and distinct choices, and the hypotheses seem almost self-defining:"在许多情况下，有两个清晰的和独特的选择，并假设看起来几乎是自定义："• Auto inspection (acceptabl e, not acceptable)• Disease (have the disease, don't)• Speed reduction of 5 mph (it happened, it didn't)• Accident reduction of 10% (it happened, it didn't)• Mode: shift by five percentage points (it happened,it didn't)"•自动检查（接受，不接受）•病害（有病害，不）•以每5英里的速度减少（它发生，它没有）•事故以10％速率减少（它发生，它没有）•模式：由五个百分点（它的发生，它没有）"Of course, there is the distinction between the real truth (reality, unknown to us) and the decision we make, as already discussed and related to Type I and Type II errors. That is, we can decide that some cars in good working order need repairing and we can decide thatsome unsafe cars do not need repairing."当然，还有的真正区别真理（现实中，我们未知的）和我们所做的决定，正如已经讨论过的相关的I型和II型错误。
也就是说，我们可以决定在一些好车\需要维修的工作秩序，我们可以决定一些不安全的车不进行修葺工程。
"There is also the distinction that people may not want to reduce the issue to a binary choice or might not be able to do so. For instance, if an engineer expects a 10% decrease in the accident rate, should we test "H o: no change" against "Hi: 10% decrease" and not allow the possibility of a 5% change? Such cases are addressed in the next section. For the present section, we will concentrate on binary choices"也有区别，人们可能不希望减少这个双重的的选择或者不能。
例如，如果一个工程师预计，事故率降低10％，我们应该测试“H0：不改变”或者反对“H1：减少10％”，而不是允许有5％的变化的可能性？这种情况将在下一节讨论。
对于本节中，我们\将集中于一对问题的选择"Application: Travel Time Decrease "应用：旅游时间缩短"Consider a situation in which the existing travel time on a given route is known to average 60 minutes, and experience has shown the standard deviation to be about 8 minutes. An "improvement" is recommended that is expected to reduce the true mean travel time to55 minutes"考虑一个情况，即有一个六十分钟的路车，经历告诉我更具有八分钟的误差。
