An auditor for a large oil corporation has taken a random sample of monthly credit card charges for 32 individual (non-corporate)accounts.She found a mean of $81.76.Assume that the population standard deviation is 48.2.A 98% confidence interval estimate for the population mean of individual credit card charges would be:
A) 81.76 $\pm$ 19.89.
B) 81.76 $\pm$ 16.72.
C) 81.76 $\pm$ 112.94.
D) 81.76 $\pm$ 22.0.
E) 81.76 $\pm$ 2.33.

Question

Quizplus · Accepted Answer

The correct answer is A because the confidence interval is calculated as:mean $\pm$ z-score * (standard deviation / square root of sample size)= 81.76 $\pm$ 2.326 * (48.2 / square root of 32)= 81.76 $\pm$ 19.89

An Auditor for a Large Oil Corporation Has Taken a Random