Assignment Problem 21 from Chapter 11 discussed the relatedness of subordinate males to breeding females in the Seychelles warbler. Five subordinates that did not help feed the offspring of the older birds were measured for their relatedness to the offspring of the breeding females, with a mean relatedness of −0.05 and a standard deviation of 0.45. Another eight subordinates that did help feed younger offspring were also measured for their relatedness to the younger birds. For these eight, the mean relatedness was 0.27, with a standard deviation of 0.45.

a. Are helpful and unhelpful subordinates different in their mean relatedness to the younger birds? Carry out an appropriate hypothesis test.

b. Find the 95% confidence interval for the difference in mean relatedness for the two classes of subordinates.

Data from problem 21

In Seychelles warblers, young adult females known as subordinates sometimes hang around the territories of older birds. Sometimes these subordinates help feed the offspring of the older birds, and sometimes not. In one study, subordinate birds that did not help were genetically assessed to discover whether they were related to the offspring of the older birds (Richardson et al. 2003). A “relatedness” score was assigned to each subordinate, with a value of zero meaning no relationship to the offspring. Out of five subordinates examined, the mean relatedness was −0.05 with standard deviation 0.45 (relatedness can be negative if by chance sampled individuals are less related than the population as a whole). What is the 95% confidence interval for relatedness of unhelpful subordinates to the offspring?