A sticker on a certain make of car states that the average miles per gallon (mpg) on the highway is 22. A consumer group took a random sample of 7 individuals who owned this make of car and asked them to report their overall gas mileage. The data are given below.
a. Make a 95% confidence interval for the overall mpg of this make of car.
b. Based on the result in part a, does it appear that the overall mpg is lower than the highway mpg of 22? Explain.