Prototype electric cars are randomly assigned to one of two charging regimens. Over the course of a three-month test period, engineers record the number of times the car was driven and the number of...

Prototype electric cars are randomly assigned to one of two charging regimens. Over the course of a three-month test period, engineers record the number of times the car was driven and the number of times it had a charging malfunction. The data is shown in Table 13.12.

(a) Do the two regimens differ in the expected number of malfunctions per drive?

(b) Why should the p values from the usual test statistics be regarded as approximate?