Chapter 6.3, Problem 2Q

Efforts to find a genetic explanation for why certain people are right-handed and others left-handed have been largely unsuccessful. Reliable data are difficult to find because of environmental factors that also influence a child’s “handedness.” To avoid that complication, researchers often study the analogous problem of “pawedness” in animals, where both genotypes and the environment can be partially controlled. In one such experiment $\left(30\right)$, mice were put into a cage having a feeding tube that was equally accessible from the right or the left. Each mouse was then carefully watched over a number of feedings. If it used its right paw more than half the time to activate the tube, it was defined to be “right-pawed.” Observations of this sort showed that 67% of mice belonging to strain $\text{A/J}$ are right-pawed. A similar protocol was followed on a sample of thirty-five mice belonging to strain $\text{A/HeJ}$. Of those thirty-five, a total of eighteen were eventually classified as right-pawed. Test whether the proportion of right-pawed mice found in the $\text{A/HeJ}$ sample was significantly different from what was known about the $\text{A/J}$v strain. Use a two-sided alternative and let 0.05 be the probability associated with the critical region.