Say we want to construct a 95% confidence interval for the difference in average highway mileage between two brands of car. Assume the data comes from independent random samples.

Be sure to check conditions, calculate the appropriate degrees of freedom (you may use either approach we discussed in class for two-sample means), identifyt*df, and show your work.

Brand A:

Sample Mean: 23

Standard deviation: 5.3

Sample: 24

Brand B:

Sample Mean: 27.8

Standard deviation: 5.0

Sample: 24