Question

R1.23: The chief operating officer wants to know if the 17th quarter’s customer satisfaction survey result, 88, “is a statistically significant improvement of the mean at the 95% confidence level and why?” The following facts apply: The data are collected by a proper survey method and are normally distributed and two-tailed. The mean satisfaction result for the last 16 quarters is 85.8. The standard deviation of the population is 3.06. The standard error calculated by the data analysis software is 0.79 (n=15) (two-tailed t-statistic is 2.13).

A. No, the mean is within the 95% confidence interval.

B. Yes. The upper limit of the 95% confidence interval for the mean is less than 88 when corrected for the use of a population instead of a sample.

C. No. The lower limit of the 95% confidence interval for the mean is greater than 88.

D. Unable to form a conclusion. To determine a statistically valid answer, at least 30 quarters of data are required.

Answer 1

A. No, the mean is within the 95% confidence interval.