Question

6.45 Fuel efficiency in metric units. In the previous
exercise, you found an estimate with a margin of error
for the average miles per gallon. Convert your estimate
and margin of error to the metric units kilometers per
liter (kpl). To change mpg to kpl, use the fact that
1 mile = 1.609 kilometers and 1 gallon = 3.785 liters.

6.44 Fuel efficiency. Computers in some vehicles
calculate various quantities related to performance. One
of these is the fuel efficiency, or gas mileage, usually
expressed as miles per gallon (mpg). For one vehicle
equipped in this way, the car was set to 60 miles per
hour by cruise control, and the mpg were recorded
at random times.13 Here are the mpg values from the
experiment:
37.2 21.0 17.4 24.9 27.0 36.9 38.8 35.3 32.3 23.9
19.0 26.1 25.8 41.4 34.4 32.5 25.3 26.5 28.2 22.1
Suppose that the standard deviation of the population of
mpg readings of this vehicle is known to be s 5 6.5 mpg.
(a) What is sx, the standard deviation of x?
(b) Based on a 95% confidence level, what is the margin
of error for the mean estimate?
(c) Given the margin of error computed in part (b), give a
95% confidence interval for m, the mean highway mpg for
this vehicle. The vehicle sticker information for the vehicle
states a highway average of 27 mpg. Are the results of this
experiment consistent with the vehicle sticker?

Answer 1