A researcher is investigating which of two newly developed automobile engine oils is better at prolonging the life of an engine. Since there are a variety of automobile engines, 20 different engine types were randomly selected and were tested using each of the two engine oils. The number of hours of continuous use before engine breakdown was recorded for each engine oil. Suppose the following 95% confidence interval for μA - μB was calculated: (100, 2500). Which of the following inferences is correct?
A) We are 95% confident that an engine using oil A has a higher mean number of hours of continuous use before breakdown than does an engine using oil B.
B) We are 95% confident that the mean number of hours of continuous use of an engine using oil A is between 100 and 2500 hours.
C) We are 95% confident that an engine using oil B has a higher mean number of hours of continuous use before breakdown than does an engine using oil A.
D) We are 95% confident that no significant differences exists in the mean number of hours of continuous use before breakdown of engines using oils A and B.

Question

Quizplus · Accepted Answer

The confidence interval is (100, 2500), which means that we are 95% confident that the true difference in the mean number of hours of continuous use before breakdown between engines using oil A and engines using oil B is between 100 and 2500 hours. Since the lower bound of the confidence interval is greater than 0, we can conclude that we are 95% confident that an engine using oil A has a higher mean number of hours of continuous use before breakdown than does an engine using oil B.

A Researcher Is Investigating Which of Two Newly Developed Automobile