Too Fast a Location? - At a particular location along a highway, a state official from the Department of Transportation in an unmarked car records the speed for each of a random sample of 36 cars. The resulting sample mean speed was 68.3 miles per hour (mph) and the standard error of the sample mean was 1.18 mph.
A. What is the value of the standard deviation for these 36 speeds?
B.Provide a 95% confidence interval to estimate the population mean car speed (for all such cars traveling along that part of the highway).
C. It is assumed that the sample of cars is randomly selected (representative). Even though the histogram and qq plot of the 36 car speeds are found to show evidence that the population of speeds at that location may not be normally distributed, can the resulting confidence interval be considered valid?