You Wish to Construct a 90% Confidence Interval to Compare

Multiple Choice

You wish to construct a 90% confidence interval to compare the mean measurement for two groups.A small pilot study yields sample standard deviations of 20 and 30 for Group 1 and Group 2,respectively.If we wish to obtain a margin of error of at most 5,what sample size should we take from each group? Assume equal sample sizes.

A) 141
B) 139
C) 143
D) 140
E) 142