More errors A corporation with a fleet of vehicles wanted to test the cost-effectiveness of using Motor Silk oil additive. For the study, 6100 delivery and passenger vehicles were tested for the same 3-month period in one year and then again in the subsequent year. In the initial year, the fleet was driven without Motor Silk. Then in the second year, Motor Silk was used according to the standard instructions. The average fuel economy increased from 18.97 mpg to 21.72 mpg.

1. What kind of a study is this?

2. Will they do a one-tailed or a two-tailed test?

3. Explain in this context what a Type I error would be.

4. Explain in this context what a Type II error would be.

5. Which type of error would the additive manufacturer consider more serious?

6. If the vehicles with the additive are indeed statistically significantly better, can the company conclude it is an effect of the additive? Can they generalize this result and recommend the additive for all cars? Explain.