Braking distances of cars. A random sample of 13 four-cylinder cars is obtained and braking distances are measured and found to have a mean of 137.5 ft. and a standard deviation of 5.8 ft. A random sample of 12 six cylinder cars is obtained and the braking distances have a mean of 136.3 ft. and a standard deviation of 9.7 ft. Use a significance level of 0.05 to test the claim that braking distances of four-cylinder cars and braking distances of six-cylinder cars have the same standard deviation.