"Hypothesis Testing

3. The director of admissions at the University of Maryland, University College is concerned about the high cost of textbooks for the students each semester. A sample of 20 students enrolled in the university indicates that X (bar) = $315.4 and s = $43.20.

a. Using the 0.10 level of significance, is there evidence that the population mean is above $300?

b. What is your answer in (a) if s = $75 and the 0.05 level of significance is used?

c. What is your answer in (a) if X (bar) = $305.11 and s = $43.20?

d. Based on the information in part (a), what decision should the director make about the books used for the courses if the goal is to keep the cost below $300?

What I THINK I know so far....

Null Hypothesis: H0<= 300

Alternate Hypothesis Ha>300

Std Dev: 43.20

Significance Level .10

x(bar)=315.40

n=20

df=19

I've been doing some confidence interval problems and I can't seem to figure out if I have to do some work with a confidence interval before I work on the hypothesis test...???