5.7. John is interested in measuring the long-term effect of speed limit changes on automobile fatality rates. His hypothesis is that the average fatality rate after the speed limit increase is higher than the average fatality rate before the speed limit increase. He collects the fatality rates before and after the highway speed limit was changed to 75 mph in a region. His data units are months and the time span is 10 years. His research design is the relationship between individuals tha