1. A hospital administrator wants to estimate the mean length of stay for all inpatients in that hospital. Based on a systematic random sample of 100 records of patients for the previous year, she knows that the sample mean was 5.3 and the standard deviation was 2.4 for this sample. a) Construct (by hand) and interpret a 95% confidence interval for the mean. b) Assume the administrator decides that this interval in a) is too wide, and she prefers one of only half this width at the same confidence level. How large a sample size is needed? Assume we know the standard deviation of the length of stay for all inpatients (i.e., population) is 1.9. 2. A public health unit wants to sample death records for the past year in Taiwan to estimate the proportion of the deaths that were due to accidents. a) Health officials want the estimate to be accurate to within 0.05 with probability of 0.99. Find the necessary sample size, if, based on previous studies, officials believe that this proportion does not exceed 0.1 请问有高手知道第一题(b)和第二题(a)要如何解吗？ 谢谢～ --

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