Gas mileage estimates for cars and light-duty trucks are determined and published by the U.S. Environmental Protection Agency (EPA). According to the EPA, "...the mileages obtained by most driverswill be within plus or minus 15 percent of the [EPA] estimates...." The mileage estimate given for one model is 23 mpg on the highway. If the EPA claim is true, the standard deviation of mileages should be about 0.15 * 23/3 = 1.15mpg.Why 0.15*23must be divided by 3?