Question

Manual-transmission cars typically average 1-2 miles per gallon better than their automatic-transmission counterparts. Assume there are about 260 million cars in the U.S. and that 90% are automatics. (a) How much gasoline would we save each year if all drivers of automatics switched to comparable manual-transmission cars? Assume an average mileage of 25 mpg for manuals and 23 mpg for automatics.

Answer #1

On the average a car travels a distance of per year .

There are cars in U.S.

Number of automatic cars are

Number of manual cars are

Mileage of automatic car is and mileage of manual car is

So the amount of usage of gasoline by an automatic car in one year is

The amount of usage of gasoline by a manual car in one year is

Total usage of gallons by automatic and manual cars is

If all the automatic cars are switched to manual cars, the usage of gasoline by all the manual cars is

Amount of gasoline save by swiching the automatic cars to manual cars is

that is million gallons can be saved.

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?
Assume that conditions for inference...

The data accompanying this exercise show miles per gallon (mpg)
for 25 cars. We can assume that the mpg are normally
distributed.
a. State the null and the alternative hypotheses in order to
test whether the variance differs from 62 mpg2.
b. Find the 95% confidence interval to determine whether the
variance differs from 62mpg2. Explain how you came to that
conclusion.
c. c. Find the two-tailed critical value, χ2α/2,df for a 99%
confidence level.
d. d. Use the critcal...

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