In a new police program, automobile owners in some neighborhoods whose cars are not normally driven between 1 A. M. and 5 A. M. can display a special decal in the cars' windows and authorize police to stop the cars during those hours to check the drivers' licenses. The theft rate for cars bearing such decals is much lower than had been usual for cars in those neighborhoods. If it is concluded from the statements above that automobile theft has been reduced by the program, which one of the following would it be most important to answer in evaluating that conclusion? ["Will owners who have placed decals on their cars'windows but who find it necessary to drive between 1 A. M. and 5 A. M. be harassed by police?", 'Are the neighborhoods in which the program has been put into effect a representative cross section of neighborhoods with respect to the types of automobiles owned by residents?', 'In how many neighborhoods is the police program operating?', 'Are owners who are cautious enough to join the program taking other special measures to protect their cars against theft?']