Lave (1990) discussed studies that had been done to test the usefulness of seat belts before and after their use became mandatory. One possible method of testing the usefulness of mandatory seat belt laws is to measure the number of fatalities in a particular region for the year before and the year after the law went into effect and to compare them. If such a study were to find substantially reduced fatalities during the year after the law went into effect, could it be claimed that the mandatory seat belt law was completely responsible? Explain.