The output of a power supply is assumed to be normally distributed. 16 observations taken at random on voltage are as follows: 10.35, 9.30, 10.00, 9.96, 11.65, 12.00, 11.25, 9.58, 11.54, 9.95, 10.28, 8.37, 10.44, 9.25, 9.38, 10.85

(a) Test the hypothesis that the mean voltage equals 12V against a two-sided alternative using =0.05.

(b) Construct a 95% confidence interval on . (c) Test the hypothesis that 2=1 using =0.05 (d) Construct a 95% two-sided confidence interval on .