Are the immune systems of more promiscuous species different from less promiscuous species. Researchers measured the mean white blood cell count (WBC count) for each species and the results are:

WBC count: less promiscuous WBC Count: more promiscuous

5.2 10.4

7.2 10.4

7.4 9.9

8.1 9.1

8.4 9.2

9.2 11.9

9.1 9.3

9.1 8.9

10.6 12.5

What is the mean difference in WBC count between less and more promiscuous species?

What is the 99% confidence interval for this difference?

Test the null hypothesis that there is no mean difference in WBC count between these species?