One of the reasons for multiple car accidents on highways is thought to be poor visibility. Recently, the National Transportation Agency (NTA) of the federal government sponsored a study of one rural section of highway in Idaho that had been the scene of several multiple-car accidents. Two visibility sensors were located near the site for the purposes of recording the number of miles of visibility each time the visibility reading is performed. The two visibility sensors are made by different companies, Scorpion and Vanguard. The NTA would like to develop 95% confidence interval estimates of the mean visibility at this location as recorded by both visibility sensors. The random sample data are in a file called Visibility . Also, comment on whether there appears to be a difference between the two sensors in terms of average visibility readings.