Fuel efficiency of manual and automatic cars: 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 at the 5% level of significane? Assume that conditions for inference are satisfied.

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Fuel efficiency of manual and automatic cars: 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 at the 5%
level of significane? Assume that conditions for inference are satisfied.
City MPG, Automatic
City MPG, Manual
Mean
16.12
19.85
SD
3.58
4.51
26
26
35
25 -
15
automatic
manual
City MPG
The hypotheses for this test are:
O Ho: Hautomatic = Pmanual
Ha: Pautomatic * Pmanual
%3D
O Ho: Hautomatic = Pmanual
Ha: Pautomatic < Pmanual
O Ho: Hautomatic = Pmanual
Ha: Hautomatic > Pmanual
The test statistic is:
(please round to two decimal places)
The p-value is:
(please round to four decimal places)
Transcribed Image Text:Fuel efficiency of manual and automatic cars: 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 at the 5% level of significane? Assume that conditions for inference are satisfied. City MPG, Automatic City MPG, Manual Mean 16.12 19.85 SD 3.58 4.51 26 26 35 25 - 15 automatic manual City MPG The hypotheses for this test are: O Ho: Hautomatic = Pmanual Ha: Pautomatic * Pmanual %3D O Ho: Hautomatic = Pmanual Ha: Pautomatic < Pmanual O Ho: Hautomatic = Pmanual Ha: Hautomatic > Pmanual The test statistic is: (please round to two decimal places) The p-value is: (please round to four decimal places)
Expert Solution
Step 1

Let μautomatic denote the average city mileage of automatic transmissions, and μmanual denote the average city mileage of manual transmissions. The test is whether there is difference between the average fuel efficiency of cars with manual and automatic transmissions in terms of their average city mileage. The hypothesis is,

Null hypothesis:

H0:μautomatic=μmanual

Alternative hypothesis:

Ha:μautomaticμmanual

The pooled variance is,

sp2=n1-1s12+n2-1s22n1+n2-2=26-13.582+26-14.51226+26-2=828.912550=16.57825

The pooled variance is 16.57825.

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