12.21 Refer to Exercise 12.6.

a Suppose  3.7 and  4.1. Do the data provide sufficient evidence to indicate a difference between and ? Assume that there are seven observations for each treatment.

Test by using  0.10.

b Refer to part (a). Find a 90% confidence interval for .

c Refer to part (a). Find a 90% confidence interval for m1.

(m1 - m2)

a m1 m2 y1 y2 m2

(m2 - m3)