Drugs that reduce emotionality make big money for drug companies. These drugs undergo extensive testing, some of which is done with animals. One common test of emotionality in rats is the number of fecal boluses that are dropped when an animal is left for 10 minutes in an open field (a 4' x 4' space). Greater emotionality is indicated by more boluses. Imagine that two drugs, aloe and vera were compared. Five rats received aloe and five received vera. The numbers below represent the number of boluses dropped in the open field. Aloe Vera
4 2
12 9
7 6
10 7
6 4

The effect size index for Data Set 10-8 is?