Q1. When do Americans decide what to make for dinner? An outline survey indicated that 74% of Americans decided either at the last minute or that day. Suppose that the survey was based on 500 respondents.
(a) Construct a 95% confidence interval estimate for the proportion of Americans who decided what to make for dinner either at the last minute or that day.
(b) Construct a 99% confidence interval estimate of the proportion of Americans who decided what to make for dinner either at the last minute or that day.
(c) Which interval is wider? Explain why this is true.
Q2. During a period of one month, a random sample of 27 approved life insurance policies is selected, and the processing time, in days, is recorded:
73 19 16 64 28 28 31 90 60 56 31
56 31 56 22 18 45 48 17 17 17 91
92 63 50 51 69 16 17
(a) In the past, the mean processing time was 45days.At the 0.05 level of significant, is there evidence that the mean processing time has changed from 45days?
(b) What assumption about the population distribution is needed in order to conduct the t test in (a)?
(c) Use a box plot to evaluate the assumption made in (b)?
(d) Do you think that the assumption needed in order to conduct the t test in (a) is valid? Explain.