7.1 Five students score 70, 75, 65, 70, and 65 on a test. Determine whether the scores are compatible with the following hypotheses:

(a) The mean is  D 75;

(b) the mean is  D 75 and the standard deviation is  D 5.

Test both hypotheses at the 95% or 68% confidence levels, assuming that the scores are Gaussian distributed.