13.3 In random samples of 25 from each of two normal populations, we found the following statistics :

(x_1 ) =63, s_1=18, n_1 " = 50" (x_2 ) =60, s_2=7, n_2 " = 45"

1. Estimate with 90% confidence the difference between the two population means.
2. Repeat part (a) changing the sample standard deviations to 41 and 15, respectively.
3. What happens when the sample standard deviations increase?
4. Repeat part (a) doubling the sample sizes.
5. Describe the effects of increasing the sample sizes"