The u. s. department of transportation provides estimated number of miles that residents of large metropolitan areas travel per day in a car. in a random sample of 50 city a residents the mean was 22 miles with a standard deviation of 4 miles, and in a random sample of 50 city b residents the mean was 28 miles with a standard deviation of 8 miles. you want to know if the mean difference in number of miles travelled per day between city a and city b is different from zero in the population.
a. what is the point estimate of the difference between the main number of miles that city a residence travel per day in the mean number of miles that city b residents travel per day? b. what is the 95% confidence interval for the difference between the two population means?