Three statisticians go duck hunting. They see a duck and the first statistician shoots, hitting two feet to the left of the duck. The second statistician shoots, hitting two feet to the right of the duck. The third statistician leaps up in joy, yelling, "We got it!"
This is an average joke. And by that, I mean that the joke is referring to the average (the middle point) of the first and second statisticians' shots. If you go exactly between a shot that is two feet to the left and a shot that is two feet to the right of a duck, you would find the duck right in the middle! This is why the third statistician expresses joy that the duck has been hit. The duck hunt in this scene comes from the 1984 video game by the same name.