A local university administers a comprehensive examination to the candidates for B.S. degrees in Business Administration. Five examinations are selected at random and scored. The scores are shown below.

Grades 80 90 91 62 77

a. Compute the mean and the standard deviation of the sample.
b. Compute the margin of error at 95% confidence.
c. Develop a 95% confidence interval estimate for the mean of the population. Assume the population is normally distributed.