A Researcher Is Investigating Which of Two Newly Developed Automobile $95 \%$

Multiple Choice

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 $\mu _ { \mathrm { A } } - \mu _ { \mathrm { B } }$ was calculated: $( 100,2500 )$ . Which of the following inferences is correct?

A) 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.
B) 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.
C) We are $95 \%$ confident that the mean number of hours of continuous use of an engine using oil $\mathrm { A }$ is between 100 and 2500 hours.
D) 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.