pUbeUIL'. 1. A sample of 249 American cars were tested and found to have a mean gas mileage of 20.1 mpg with a sample standard deviation of 6.41 mpg. A sample of 79 Japanese cars were sampled and found to have a sample mean of 30.01 mpg with a sample standard deviation of 6.11 mpg. Is this sufficient evidence to conclude that the gas mileage of Japanese cars is higher than the gas mileage for American cars