07-06-12

 07-06-12

Exercise in confidence intervals for the mean (standard deviation known or sample size greater than or equal to 30)

1.      Find each.

a.       Za/2 for the 99% confidence interval

b.      Za/2 for the 98% confidence interval

c.       Za/2 for the 95% confidence interval

d.      Za/2 for the 90% confidence interval

e.       Za/2 for the 94% confidence interval

2.       A university dean wishes to estimate the average number of hours hi part-time instructors teach per week.  The standard deviation from a previously study is 2.6 hours.  How large a sample must be selected if he wants to be 99% confident of finding whether the true mean differs from the sample mean buy 1 hour?

BY: JOREY MARK MILLAMENA