Suppose that we define the following events:

C = event that a randomly selected driver is observed to be using a cell phone

A = event that a randomly selected driver is observed driving a passenger automobile

V = event that a randomly selected driver is observed driving a van or SUV

T = event that a randomly selected driver is observed driving a pickup truck

The probabilities given below are based on data from the National Highway Traffic Safety Administration (“Traffic Safety Facts,” February 2014):

P(C) = 0.015 P(C|A) = 0.017

P(C|V) = 0.014 P(C|T) = 0.010

Explain why P(C ) is not just the average of the three given conditional probabilities.