Discussion:
Q: Studies show that gasoline use for the hybrid cars that are sold in the United States is normally distributed with a mean of 51.7 miles per gallon (mpg) for 2002. A random sample of 49 of the newer hybrid cars is tested in 2004 and found to have an average of 54.2 mph on the highway and a standard deviation of 4.5 mpg. Is this sufficient evidence to conclude that the mean mpg is higher in the newer cars? Test the appropriate hypothesis using alpha = 0.05. Use the traditional method approach.