A study of 45 professors showed that the average time they spent creating test questions was 15.5 minutes per question. The standard deviation of the population is 5.8. Which of the following is the 98% confidence interval for the average number of minutes it takes to create a test question?

Question

Quizplus · Accepted Answer

Using the formula for a confidence interval for a population mean, we can calculate the margin of error to be:

ME = z*(sigma/sqrt(n)) = 2.33*(5.8/sqrt(45)) = 2.70

where z is the z-score for a 98% confidence interval (which we can look up in a table or use a calculator to find).

Then, the confidence interval for the population mean is:

x̄ ± ME = 15.5 ± 2.70

which gives us the interval (12.80, 18.20).

Therefore, choice C is the correct answer as it contains the correct range of values.

A Study of 45 Professors Showed That the Average Time