The number of miles that the brake pads in a population of cars last is normally distributed. In a sample of 51 cars, the brake pads lasted a mean of 38.3 thousand miles with a standard deviation of 9.2 miles.
1. With .10 significance test the claim that the standard deviation in the number of miles that the brake pads last is less than 10 thousand. Use the critical value method and chart.
2. With .01 significance, test the claim that the mean number of miles that the brake pads last is more than 35 thousand. Use the critical value method and chart.
3. With .05 significance, test the claim that the mean number of miles that the brake pads last is 40 thousand if the population standard deviation is known to be 10.8 thousand. Use the P-value