Question: Confidence intervals

Dr. Kittleson is concerned that the students’ grade point averages have changed dramatically in recent years. The graduating senior’s GPA over the past five years was 2.75. Dr. Kittleson randomly sampled 256 seniors from the last graduating class and found the GPA average was 2.85 with s = 0.65.

You need to do 2 things:

(a) Test the following hypothesis:

Null hypothesis:

There is no significant difference between GPAs during the past five years.

Alternative Hypothesis:

There has been an increase in GPAs over the past five years.

(b) Find the confidence interval (CI ₉₅)