1) For a random sample of 200 students, the mean cost for textbooks during the first semester of college was found to be $368.75, and the sample standard deviation was $35.43. Assuming that the population is normally distributed, find the margin of error of a 80% confidence interval for the population mean.

a) The margin of error for an 80% confidence interval is _____.

2) A clinic offers a weight-loss program. The table below gives the amounts of weight loss, in pounds, for a random sample of 20 of its clients at the conclusion of the program. Assume that the data are normally distributed. Complete parts (a) and (b).

16	25	30	8	18	13	21	17	12	8
16	8	13	8	20	23	11	20	11	20

a) Find a 99% confidence interval for the population mean.

The 99% confidence interval is from a lower limit of _______ to an upper limit of _____.

(Round to two decimal places as needed.)

b) Without doing the calculations, explain whether a 95% confidence interval for the population mean would be wider than, narrower than, or the same as that found in part (a). Choose the correct answer below.

A. It will be wider because the reliability factor will be smaller for a 95% confidence interval than for a 99%

confidence interval.

B. It will be wider because the reliability factor will be larger for a 95% confidence interval than for a 99%

confidence interval.

C. It will be the same because the confidence interval is being calculated for the same data set.

D. It will be narrower because the reliability factor will be smaller for a 95% confidence interval than for a

99% confidence interval.