A 95 confidence interval is constructed for the population m

A 95% confidence interval is constructed for the population mean revenue. If the data from the last 40 days had been used, then the resulting 95% confidence intervals would have been ________________.

A. Wider, with a larger probability of reporting an incorrect interval.

B. Wider, with the same probability of reporting an incorrect interval.

C. Narrower, with a larger probability of reporting an incorrect interval.

D. Narrower, with the same probability of reporting an incorrect interval.

Solution

Confidence Interval
CI = x ± Z a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval

Sample size is indirect propotional to the confidence interval compute, increasing the sample narrower the width of the interval

ANS:

C. Narrower, with a larger probability of reporting an incorrect interval.