Chapter 3 regen According to the 6895997 rule we expect 68 o

Chapter 3 regen

According to the 68-95-99.7 rule, we expect 68% of the observations in the data set to fall
between  and .

15. The lengths of pregnancies in a small rural village are Normally distributed with a mean of 264 days and a standard deviation of 14 days.

We expect that 68% of pregnancies will last
between  and  days.

16. The physical plant at the main campus of a large state university receives daily requests to replace florescent light-bulbs. The distribution of the number of daily requests is Normally distributed with a mean of 45 and a standard deviation of 7. Using the Empirical Rule, what is the approximate percentage of light-bulb replacement requests numbering between 38 and 45?

Do not enter the percent symbol.
ans =  %

17. The number of potholes in any given 1-mile stretch of freeway pavement in Pennsylvania has a Normal distribution. This distribution has a mean of 43 and a standard deviation of 10. Using the Empirical Rule, what is the approximate percentage of 1-mile long roadways with potholes numbering between 23 and 73?

%

18. 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 Normally distributed with a mean of 44 months and a standard deviation of 9 months. Using the Empirical Rule, what is the approximate percentage of cars that remain in service between 26 and 35 months?

Do not enter the percent symbol.
ans =  %

Solution

13) P for 0.2 and 0.7 = 0.5

14)68% of the observations in the data set to fall
between 5.8 and 8.0

15) (250, 278)

16) Between 38 and 45, 34%

17) 0.97 or 97%

18) 14.5%