Small falcons in Sweden. Often the percent of an animal species in the wild that survives to breed again is lower following a successful breeding season. This is part of nature's self-regulation, tending to keep population size stable. A study of merlins (small falcons) in northern Sweden observed the number of breeding pairs in an isolated area and the percent of males (banded for identification) who returned the next breeding season. Here are data for nine years:

Pairs: 28 29 29 29 30 32 33 38 38

Percent: 82 83 70 61 69 58 43 50 47

(a) Why is the response variable the percent of males that return rather than the number of males that return?

(b) Make a scatterplot. To emphasize the pattern, also plot the mean response for years with 29 and 38 breeding pairs and draw lines connecting the mean responses for the six values of the explanatory variable

(c) Describe the pattern. Do the data support the theory that a smaller percent of birds survive following a successful breeding season?