A company in Maryland has developed a device that can be attached to car engines,which it believes will increase the miles per gallon that cars will get.The owners are interested in estimating the difference between mean mpg for cars using the device versus those that are not using the device.The following data represent the mpg for random independent samples of cars from each population.The variances are assumed equal and the populations normally distributed. Given this data,what is the upper limit for a 95 percent confidence interval estimate for the difference in mean mpg?
A)Approximately 3.88 mpg
B)About 5.44 mpg
C)Just under 25.0
D)None of the above.

Question

A company in Maryland has developed a device that can be attached to car engines,which it believes will increase the miles per gallon that cars will get.The owners are interested in estimating the difference between mean mpg for cars using the device versus those that are not using the device.The following data represent the mpg for random independent samples of cars from each population.The variances are assumed equal and the populations normally distributed.  Given this data,what is the upper limit for a 95 percent confidence interval estimate for the difference in mean mpg?
A)Approximately 3.88 mpg 
B)About 5.44 mpg 
C)Just under 25.0 
D)None of the above.

Quizplus · Accepted Answer

Using a two-sample t-test with equal variances and a 95% confidence level, the point estimate for the difference in means is 4.66 mpg. The margin of error is calculated as 0.78 mpg. Adding this to the point estimate gives an upper limit of approximately 5.44 mpg. Therefore, the answer is B.

A Company in Maryland Has Developed a Device That Can