Fuel economy estimates for automobiles built one year predicted a mean of

24.2

mpg and a standard deviation of

6.8

mpg for highway driving. Assume that a Normal model can be applied. Use the

689599.7

Rule to complete parts a) through e).

a)	Draw the model for auto fuel economy.

A.

17.4

10.6

3.8

37.8

31

44.6

24.2

68%

95%

99.7%

A bell-shaped curve with horizontal axis from less than 3.8 to 44.6 plus in intervals of 6.8 begins just above the horizontal axis, increases at an increasing and then decreasing rate to its maximum at 24.2, and decreases at an increasing and then decreasing rate approaching the horizontal axis. The curve is symmetric. The area below the curve is subdivided into regions by the intervals and labeled as follows: from 17.4 to 31, "68%"; from 10.6 to 37.8, "95%"; from 3.8 to 44.6, "99.7%."

B.

17.4

10.6

3.8

51.4

37.8

65

24.2

68%

95%

99.7%

A bell-shaped curve with horizontal axis from less than 3.8 to 65 plus begins just above the horizontal axis, increases at an increasing and then decreasing rate to its maximum at 24.2, and decreases at an increasing and then decreasing rate approaching the horizontal axis. The seven equidistant horizontal axis labels are as follows from left to right: 3.8, 10.6, 17.4, 24.2, 37.8, 51.4, 65. The curve is visually symmetric. The area below the curve is subdivided into regions by the intervals and labeled as follows: from 17.4 to 37.8, "68%"; from 10.6 to 51.4, "95%"; from 3.8 to 65, "99.7%."

C.

20.8

17.4

14

31

27.6

34.4

24.2

68%

95%

99.7%

A bell-shaped curve with horizontal axis from less than 14 to 34.4 plus in intervals of 3.4 begins just above the horizontal axis, increases at an increasing and then decreasing rate to its maximum at 24.2, and decreases at an increasing and then decreasing rate approaching the horizontal axis. The curve is symmetric. The area below the curve is subdivided into regions by the intervals and labeled as follows: from 20.8 to 27.6, "68%"; from 17.4 to 31, "95%"; from 14 to 34.4, "99.7%."

b)	In what interval would you expect the central 99.7% of autos to be found?

Using the 68-95-99.7 rule, the central

99.7%

of autos can be expected to be found in the interval from

enter your response here

to

enter your response here

mpg.

(Do not round. Type integers or decimals.)

c)	About what percent of autos should get more than 31 mpg?

Using the 68-95-99.7 rule, about

enter your response here%

of autos should get more than

31

mpg.

(Do not round. Type an integer or a decimal.)

d)	About what percent of autos should get between 31 and 37.8 mpg?

Using the 68-95-99.7 rule, about

enter your response here%

of autos should get between

31

and

37.8

mpg.

(Do not round. Type an integer or a decimal.)

e)	Describe the gas mileage of the worst 2.5% of cars.

Choose the correct answer below.

A.

They get more than

31

mpg.

B.

They get

less

than

10.6

mpg.

C.

They get less than

17.4

mpg.

D.

They get

less

than

3.8

mpg.