An imaginary researcher examined the 18 largest mammal species in the Americas that occur both on the mainland and on islands. Sixteen of the mammal species were smaller on islands than on the mainland, such as the adult Channel Island pygmy mammoth shown next to a modern human in the drawing. The remaining two species were larger on the islands than on the mainland. With these data, test whether large mammals are likely to differ in size between islands and the mainland in a particular direction.

Proceed through all four steps of the hypothesis-testing procedure. Use the null sampling distribution in Table 6.2-1 to calculate your P-value.  Apply the conventional significance level, α=0.05. 

Table 6.2-1