CHAPTER 8 SOLUTIONS AND MINIPROJECT NOTES
CHAPTER 8
BELLSHAPED CURVES AND OTHER SHAPES
EXERCISE SOLUTIONS
8.1
a.
16%
b.
97.5%
c.
80%
8.2
a.
1
−
0.9 = 0.1, or 10%
b.
1
−
0.4 = 0.6, or 60%
c.
1
−
0.99 = 0.01, or 1%
8.3
a.
−
0.67
b.
0.67
c.
−
0.13
d.
2.05
8.4
a.
2.05 (same as 98% below).
b.
0.00 (same as 50% below).
c.
−
0.67 (same as 25% below).
d.
1.28 (same as 90% below).
8.5
a.
84%
−
16% = 68%.
b.
96%
−
10% = 86%.
c.
84%
−
50% = 34%.
8.6
a.
The standardized score is (116
−
100)/16 = 1.00; by Table 8.1 this is the 84th percentile.
b.
Both pictures are identical bellshaped curves. The top picture should be centered at 100 and have a line
at 116, with 84% of the area below the line at 116 and 16% of the area above it. The bottom picture should
look identical, except it is centered at 0 and has the line at 1 instead of 116.
8.7
The picture should show a bellshaped curve centered on 100. The interval from 90 to 110 should
encompass 68% of the area, from 80 to 120 should encompass 95% of the area, and 70 to 130 should
encompass 99.7% of the area.
8.8
a.
The standardized score is (450
−
497)/115, or about
−
0.41, which is the 34th percentile.
b.
The standardized score is (92
−
100)/16 =
−
0.5, which is the 31st percentile.
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 '08
 SEIFRIEDTHOMASJ
 Standard Deviation, 1%, 75%, 2%, 80%, 86%

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