The National Quality Research Center at the University of Michigan provides a quarterly measure of consumer opinions about products and services. A survey of 50 restaurants in the Fast Food/Pizza group showed a sample mean customer satisfaction index of 59. Past data indicate that the population standard deviation of the index is 4.

a) What is the name of the variable?

b) What is the point estimate of the population variance?

c) Using 95% confidence, what is the margin of error?

d) Using the 90% confidence, find the confidence interval of the population mean. Find the good samples and bad samples area of this confidence interval using a curve.

e) Find expected number of good samples according to the above curve.