An automobile manufacturer needs to estimate the average highway fuel economy miles per gallon for a new truck that will be sold starting next year A random sample of 148 trucks were tested for highway fuel economy and the sample had a mean of 28 5 miles per gallon with a standard deviation of 2 5 miles per gallon Using a 95 confidence level determine the margin of error E and a confidence interval for the average highway fuel economy of this new truck Report the confidence interval using interval notation Round solutions to two decimal places if necessary The margin of error is given by E A 95 confidence interval is given by