An automobile manufacturer claims their car gives 30.0 miles/gallon (mpg). An independent testing firm has been contracted to test the mpg of the car. They tested 15 vehicles. The sample mean is 31.533 mpg, and the sample stand deviation is 2.875 mpg. They suspect that the cars' mpg performance is even better than what the manufacturer claims; and the true mean mpg may be over 30. Is there sufficient evidence, at the 0.05 significance level, that the cars' performance is better than their manufacturer's mpg rating?
- What are the null hypothesis and alternative hypothesis for this test?
- The decision rule, based on the critical value, is: to reject Ho if the calculated test statistic is?
- What is the calculated test statistic to test the hypothesis?