Question

1) A company has a policy of retiring company cars; this policy looks at number of miles driven, purpose of trips, style of car and other features. The distribution of the number of months in service for the fleet of cars is bell-shaped and has a mean of 57 months and a standard deviation of 11 months. Using the empirical rule, what is the approximate percentage of cars that remain in service between 24 and 46 months?

Do not enter the percent symbol.
ans = %

2)A sample of size n=10n=10 is drawn from a population. The data is shown below.

131.9	121.7	104.5	97.3	117.8
131.9	131.9	114.1	119.8	109

What is the range of this data set?

range =

What is the standard deviation of this data set? (Remember, it is a sample.) Please report the answer with appropriate rounding, reporting 2 more decimal places than the original data. Please, please, please do not calculate the value by hand.

stdev =

Answer 1

This is a normal distribution question with

P(24.0 < x < 46.0)=?

This implies that
P(24.0 < x < 46.0) = P(-3.0 < z < -1.0) = P(Z < -1.0) - P(Z < -3.0)
P(24.0 < x < 46.0) = 0.1587 - 0.0014
P(24.0 < x < 46.0) = 0.1573

Since we know that
The range is the difference between the largest and smallest values in a set of values.
This implies that
Range = 131.9-97.3
Range = 34.6
Since we know that

Where n is the number of data points
Now

and n = 10
This implies that

Since we know that

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