课程名称：统计学 课程性质：整开 课程范围：ch7-10 开课教师：陈心苹 开课学院： 开课系级： 考试日期(年月日)：99/01/14 考试时限(Mins)：2hrs 先声明，这份试题的英文错误实在是有点多.... 以下有变色的之後的是我找到比较明显的错误 大家可以来一起抓错误~ 试题本文： 1.(10%) In a population of 4000 employees, a simple random sample of 100 employees is selected in order to estimate the mean age for the population. The population standard deviation is σ=7.2 years. What is the probability that the sample mean age of the employees will be within(plus or minus)6.5 years of the population age? 2.(15%)An geneticist wishes to estimate the average weight of men for certain race of people. If the population standard deviation is assumed to be 3 pounds and if she randomly samples 40 men. a. Find the probability that the difference (缺between) the sample mean and the true population mean will not exceed 0.7 pounds. b. Suppose that the geneticist wants the difference (缺between) the sample mean and the population mean to be less than 0.45 pounds, with the probability 0.95. How many men should he sample to achieve this objective? 3.(15%) A random sample of 35 people employed by Florida state authority established they earned an average wage (including benefits) of ＄65.00 per hour. The sample standard deviation was ＄6.25 per hour. a. Develop a 95 percent confidence interval for the population mean wage (including benefits) for these employees. b. How large a samole is needed to assess the population mean with an allowable error of ＄1.50 at 99 percent confidence? 4.(10%) These are 2000 eligible voters in York County, South Carolina. A random sample of 400 York County voters revealed 250 plan to vote to return Louella Miller to the state senate. Construct a 99 percent confidence interval for the proportion of voters in the county who plan for Ms. Miller. 5.(15%) Recent studies indicate that the typical 50-year-old woman spends ＄350 per year for personal-care products. The distribution of the amounts spent follows a normal distribution with a stardard deviation of ＄45 per year. We select a random samole of 20 women. The mean amount spent for those sampled is ＄335. a. What is the likelihood of finding a sample mean this(应该是is) large or larger from(我觉得是than) the specified population? b. Can we accept the result from recent studies at the 0.05 significance level? 6.(10%) A recent survey of 50 executive who were laid off from their previous position revealed it took a mean of 26 weeks for them to find another position. The standard deviation of the sample was 6.2 weeks. Construct a 99 percent confident interval for the population mean.Is it reasonable that the population mean is 28 weeks? Justify your answer. 7.(15%) Information from the American Institute of Insurance indicates the mean amount of life insurance per household in the United States is ＄100,000. This distribution is positively skewed. The standard deviation of the population is not known. a.Suppose that you selected 50 samples of households. What is the expected shape of the distribution of the sample mean? b.Find the likelihood of selecting a sample with a mean of more than＄90,000 but less than＄102,000.2.(我总觉得这句文法有哪里错了) 8. One of the major U.S. tire makers wishes to review its warranty for their rainmaker tire. The warranty is for 40,000 miles. The tire company believes that the tire actually lasts more than 40,000 miles. A sample 49 tires revealed that the mean number of miles is 45,000 miles with a standard deviation of 15,000 miles. Test the hypothesis with a 0.05 significance level. If the actual true tire mileage is 42,000 miles, what is the probability of a Type II error? ※ 编辑: traintrain 来自: 118.168.88.156 (01/16 22:12)