The Grants' Finch Complete Beak Data.
The data file ex0218 contains the beak depths (in mm) of all 751 finches captured by Peter and Rosemary Grant in 1976 and all 89 finches captured in 1978 (as described in Section 2.1.1). Use a statistical computer program for parts a-d:
(a) Draw side-by-side box plots of the two groups of beak depths.
(b) Use the two-sample t -test on these data to find the one-sided p-value for a test of the hypothesis of no difference in means against the alternative that the mean in 1978 is larger.
(c) What is the two-sided p-value from the t -test?
(d) Provide an estimate and a 95% confidence interval for the amount by which the 1978 mean exceeds the 1976 mean.
(e) What is it about the finches in the two populations that might make you question the validity of the independence assumption upon which the two-sample t -test is derived?