A new highway has just been completed and the government must decide on speed limits. There are several possible choices. However, on advice from police who monitor traffic the objective was to reduce...

A new highway has just been completed and the government must decide on speed limits. There are several possible choices. However, on advice from police who monitor traffic the objective was to reduce the variation in speeds, which it is thought to contribute to the number of collisions. It has been acknowledged that speed contributes to the severity of collisions. It is decided to conduct an experiment to acquire more information. Signs are posted for 1 week indicating that the speed limit is 70 mph. A random sample of cars’ speeds is measured. During the second week, signs are posted indicating that the maximum speed is 70 mph and that the minimum speed is 60 mph. Once again a random sample of speeds is measured. Can we infer that limiting the minimum and maximum speeds reduces the variation in speeds?