Salaries of Ph.D. Students

4.   Salaries of Ph.D. Students Full-time Ph.D. students receive an average salary of $12,837 according to the

U.S. Department of Education. The dean of graduate studies at a large state university feels that Ph.D. students in his state earn more than this. He surveys 44 randomly selected students and finds their average

salary is $14,445, and the population standard deviation is $1500. With a = 0.05, is the dean correct?

Source: U.S. Department of Education/Chronicle of Higher Education.

5.   Health Care Expenses The mean annual expenditure per 25- to 34-year-old consumer for health care is $1468. This includes health insurance, medical services, and drugs and medical supplies. Students at a large university took a survey, and it was found that for a sample of

60 students, the mean health care expense was $1520, and the population standard deviation is $198. Is there sufficient evidence at a = 0.01 to conclude that their health care expenditure differs from the national average of $1468? Is the conclusion different at a = 0.05?