Fuel efficiency of manual and automatic cars, Part I: Each year the US Environmental Protection Agency (EPA) releases fuel economy data on cars manufactured in that year. Below are summary statistics on fuel efficiency (in miles/gallon) from random samples of cars with manual and automatic transmissions manufactured in 2012. Do these data provide strong evidence of a difference between the average fuel efficiency of cars with manual and automatic transmissions in terms of their average city mileage? Assume that conditions for inference are satisfied.
City MPG, Automatic City MPG, Manual
Mean 16.12 19.85
SD 3.58 4.51
n 26 26
The hypotheses for this test are:
- Ho: μautomatic = μmanual
- Ha: μautomatic ≠ μmanual
- Ho: μautomatic = μmanual
- Ha: μautomatic > μmanual
- Ho: μautomatic = μmanual
- Ha: μautomatic < μmanual
The test statistic is: ___________________ (please round to two decimal places.)
The p-value is: ___________________ (please round to four decimal places and use the following formula for the degrees of freedom: (n1 - 1) + (n2 - 1))
Interpret the result of the hypothesis test in the context of the problem:
a. The data do not provide sufficient evidence that there is a difference between the average fuel efficiency of manual and automatic cars in terms of their average city mileage
b. The data provide sufficient evidence that there is no difference between the average fuel efficiency of manual and automatic cars in terms of their average city mileage
c. The data provide sufficient evidence that there is a difference between the average fuel efficiency of manual and automatic cars in terms of their average city mileage