Answer Happy

The manufacturer of a gasoline additive claims that the use of this additive increases gasoline mileage. A random sample of six cars was selected, and these cars were driven for 1 week without the gasoline additive and then for 1 week with the gasoline additive. The following table gives the miles per gallon for these cars without and with the gasoline additive. Without 24.6 28.3 With 26.3 31.7 18.9 18.2 23.7 25.3 15.4 18.3 29.5 30.9 Assume that the population of paired differences is (approximately) normally distribution. Construct a 99% confidence interval for the mean of the population paired differences, where a paired difference is equal to the miles per gallon without the gasoline additive minus the miles per gallon with the gasoline additive.