Statistics classwork

According to the 2003-2004 annual report of the Association of Medical and Graduate Departments of Biochemistry, the average stipend for a postdoctoral trainee in biochemistry was $31,331 with a population standard deviation of $3,942. Treating this as the population, assume that you asked the 8 biochemistry postdoctoral trainees at your institution what their annual stipend was and that it averaged $34,000.

a. Construct a 90% confidence interval for this sample mean.

b. Construct a 95% confidence interval for this sample mean.

c. Construct a 99% confidence interval for this sample mean.

d.  Which of the three confidence intervals do you find the most helpful? Why?