Refer to the cortex-weight data of Exercise 8.4.4.
(a) Use a goodness-of-fit test to test the hypothesis that the environmental manipulation has no effect. As in Exercise 8.4.4, use a directional alternative and let α = 0.05. (This exercise shows how, by a shift of viewpoint, the sign test can be reinterpreted as a goodness-of-fit test. Of course, the chi-square goodness-of-fit test described in this chapter can be used only if the number of observations is large enough.)
(b) Is the number of observations large enough for the test in part (a) to be valid?