You want to figure out if there is a difference in lengths between male and female kestrels (kestrels are small falcons found all over Northern Virginia). You catch 12 females and 10 males with the following results (in cm):

Females: 27.7 25.4 26.4 28.5 27.4 28.0 28.7 26.7 25.6 25.3 27.5 27.8

Males: 20.3 24.1 24.1 24.6 23.2 22.4 23.2 21.2 24.2 19.1

(a) Is there a difference in lengths? Use = .01. Note that you have to calculate everything yourself.

(b) Repeat (a), but this time assume a one sided (=directional) alternative hypothesis. In kestrels (and many other hawks), females are usually larger than males.