Section S.5 – Solutions to the Practice Problems

1. 61

2. 50%

3.

4.

5.

6. Distribution B has a wider spread along the horizontal axes, because it has a larger standard deviation. The spread of the distribution curve is determined by the standard deviation. The larger the standard deviation, the larger the spread of the distribution curve.

7. 68%

8. 95%

9. 4.7%

10. About 1 standard deviation above and below the mean. 68% of the data lies between 12 and 18.

11. About 2 standard deviations above and below the mean. 95% of the data lies between -5 and -1.

12. 49.85%

13. 34%

14. 27%

15. 31.7%

16.
a. 145
b. 70
c. 82.5
d. 195

17.
a. 5.75 to 9.25
b. 4 to 11
c. 2.25 to 12.75

18.
a. 68%
b. 95%
c. 34%
d. 47.5%
e. 47.5%
f. 34%
g. 49.85%
h. 49.85%
i. 16%
j. 2.5%
k. 2.5%
l. 16%

19.
a. 84%
b. 2.5%
c. 0.15%
d. 97.5%
e. 16%
f. 84%
g. 97.5%
h. 68%
i. 16%
j. 47.5%
k. 99.85%

20.
a. 95%
b. 68%
c. 47.5%
d. 34%
e. 16%
f. 2.5%
g. 2.5%
h. 16%
i. 0.15%
j. 0.15%