79 Whales entangled in fishing gear. Refer to the Marine Mammal Science (April 2010) study of whales entangled in fishing gear, Exercise 15 . These entanglements involved one of three types of fishing gear: set nets, pots, and gill nets.

Consequently, the researchers used gear type as a predictor of the body length ( y , in meters) of the entangled whale.

Consider the regression model, E(y) = b0 + b1x1 + b2x2, where x1 = 51 if set net, 0 if not6 and x2 = 51 if pots, 0 if not6. [ Note : Gill nets is the “base” level of gear type.]

a. The researchers want to know the mean body length of whales entangled in gill nets. Give an expression for this value in terms of the b ’s in the model.

b. Practically interpret the value of b1 in the model.

c. In terms of the b ’s in the model, how would you test to determine if the mean body lengths of entangled whales differ for the three types of fishing gear?