The National Highway System Designation Act was signed into law in the United States on November 28, 1995. Among other things, the act abolished the federal mandate of 55-mile-per-hour maximum speed limits on roads in the United States and permitted states to establish their own limits. Of the 50 states (plus the District of Columbia), 32 increased their speed limits either at the beginning of 1996 or sometime during 1996. Shown in Display 2.17 are the percentage changes in interstate highway traffic fatalities from 1995 to 1996. What evidence is there that the percentage change was greater in states that increased their speed limits? How much of a difference is there? Write a brief statistical report detailing the answers to these questions. (Data from “Report to Congress: The Effect of Increased Speed Limits in the Post-NMSL Era,” National Highway Traffic Safety Administration, February, 1998; available in the reports library at http://www-fars.nhtsa.dot.gov/.)

  

      

Number of traffic fatalities in 50 U.S. states and the District of Columbia, and status of speed limit change in the state (retained 55 mph limit or increased speed limit); first 5 of 51 rows DISPLAY 2.17 ITTIT State Fatalities1995 Fatalities1996 PetChange SpeedLimit Alabama I114 1146 2.87 Inc Alaska 87 81 -6.9 Ret Arizona 1035 994 -3.96 Inc Arkansas 631 615 -2.54 Inc California 4192 3989 -4.84 Inc