Dr. Thomas Bilski is a primary care physician with a practice that is currently serving 280 patients. Dr. Bilski would like to administer a survey to his patients to measure their satisfaction levels with his practice. A random sample of 24 patients had an average satisfaction score of 8.4 on a scale of 1– 10. The sample standard deviation was 1.9.

a. Construct a 90% confidence interval to estimate the average satisfaction score for Dr. Bilski’s practice.

b. What assumption needs to be made for this analysis?

c. Verify your results with PHStat.