1) A study of estrogen levels in two different groups of women finds the following results (in pg/mL):

Group A: 18.7 20.6 20.7 19.7 19.9 19.4 20.2 21.6 18.8 14.1 21.6 16.2 21.7 20.8 19.3 21.3 1 9.9 20.8 23.2

Group B: 15.2 36.2 27.5 4.7 24.5 29.4 25.9 62.8

Some summary statistics to help you:

_

y s n

Group A: 19.921 2.0457 19

Group B: 28.275 16.9169 8

Is there a difference in estrogen levels? (Note:d.f.= 7.0864 for Welch'st-test). Use= 0.05.

2) Repeat (1), but this time assume equal variances. Use the same level ofyou used before.

3) Now let's compare the tests from problems (1) and (2)

(a) Which test (problem (1) or problem (2)) lets you reject the null hypothesis?

(b) Which test do you *think* has more power?

Usually, but not always(!!), the test with the most power has a lowerp-value.

(c) If you don't know that the population variances are equal, which test should you use?

(d) Which testshouldyou use here? (Do you know if the population variances are equal?)