Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

APPENDIX C | Solutions for Odd-Numbered Problems in the Text 665
17.
a. The percentile rank for X = 2.5 is 35%
b. The percentile rank for X = 4.5 is 90%
c. The 15th percentile is X = 1.5.
d. The 65th percentile is X = 3.5.
19. a. 26%
X f cf c%
5 2 20 100
4 5 18 90
3 6 13 65
2 4 7 35
1 3 3 15
b. 48%
c. X = 5.7
d. X = 8.0
21. a. 97%
23.
25.
b. 70.8%
c. X = 5.75
d. X = 12.83
1 978368
2 35654475
3 2046
4 4793
5 12
1 4916
2 58223
3 692437
4 77294
5 2875
6 5
CHAPTER 3
Central Tendency
1. The mean is 32
8 = 4, the median is 4.5, and the mode
is 5.
3. For this sample, the mean is 39
14 = 2.79, the median is
2.5, and the mode is 1.
5. a. Median = 5
b. Median = 4.83
7. ΣX = 96.
9. The first sample has ΣX = 84 and the second has
ΣX = 96. The combined sample has n = 20 and
ΣX = 180. The combined sample mean is M = 9.
11. a. The combined sample mean is M = 7.5.
(20 1 60)
b. The combined sample mean is 10 = 8.
(30 1 40)
c. The combined sample mean is 10 = 7.
13. The original sample has n = 7 and ΣX = 112. The
new sample has n = 7 and ΣX = 126. The new mean
is M = 18.
15. The original sample has n = 7 and ΣX = 63. The
new sample has n = 8 and ΣX = 64. The new mean
is M = 8.
17. The original sample has n = 15 and ΣX = 90. The
new sample has n = 16 and ΣX = 112. The new mean
is M = 7.
19. The original sample has n = 7 and ΣX = 35.
The new sample has n = 8 and ΣX = 48. The total
increased by 13 points, so X = 13.
21. The original sample has n = 9 and ΣX = 117.
The new sample has n = 10 and ΣX = 120. The score
that was added must be X = 3.
23. a. For treatment 1 the mean is M = 9 and for
treatment 2 the mean is M = 7. Based on the
means, the scores are higher in treatment 1.
b. For treatment 1 the median is 6.5 and for
treatment 2 the median is 7.5. Based on the
medians, the scores are higher in treatment 2.
c. Both treatments have a mode of 6. Based on
the mode, there is no difference between the
two treatments.
25. The participants were able to withstand the pain for
M = 694
10 = 69.4 seconds when they were swearing
comparing to M = 554
10 = 55.4 seconds when
yelling a neutral word. Swearing does appear to help
improve pain tolerance.
CHAPTER 4
Variability
1. a. SS is the sum of squared deviation scores.
b. Variance is the mean squared deviation.
c. Standard deviation is the square root of the
variance. It provides a measure of the standard distance
from the mean.