Discussion:
Refer to the accompanying Minitab display of a 95% confidence interval generated using the methods of this section. The sample display results from using a random sample of speeds of drivers ticketed on a section of Interstate 95 in Connecticut.
Variable N Mean StDev SE Mean 95% CI
Speed 81 67.3849 3.3498 0.3722 (66.6554, 68.1144)
Q. Ages of Motorcyclists Killed in Crashes. A study of the ages of motorcyclists killed in crashes involves the random selection of 150 drivers with a mean of 37.1 years (based on data from the Insurance Institute for Highway Safety). Assuming that = 12.0 years, construct a 99% confidence interval estimate of the mean age of all motorcyclist killed in crashes. If the confidence interval limits do not include ages below 20 years, does it mean that motorcyclists under the age of 20 rarely die in crashes?