Chapter 13 Notes Examples
Page 1 of 4
Illustration of “689599.7” Rule
4
3
2
1
0
1
2
3
4
34%
34%
13.5%
13.5%
2.35%
2.35%
0.15%
0.15%
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Chapter 13 Notes Examples
Page 2 of 4
Example
If the scores on a test have a symmetric distribution with a mean of 78.4 and a standard deviation
of 9.6, within what interval would approximately 95% of the scores fall?
≈
95% of data between
s
x
2
±
78.4 ± 2(9.6)
78.4 ± 19.2
(59.2, 97.6)
Approximately what percentage of scores will be greater than 68.8?
34% + 50% = 84%
Question
We have the IQ test scores of all seventh graders in a rural Midwest school (n = 74).
The
distribution of the scores is approximately normal with a mean of 111 and a standard deviation of
11 (A stemplot of these scores is given in figure 13.13 on page 281).
Using the 689599.7 rule,
Between what values do the IQ scores of 95% of all rural Midwest seventh graders lie?
A. (100,122)
B. (89, 133)
C. (78, 144)
Example
We have the IQ test scores of all seventh graders in a rural Midwest school (n = 74).
The
distribution of the scores is approximately normal with a mean of 111 and a standard deviation of
11 (A stemplot of these scores is given in figure 13.13 on page 281).
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '07
 JOHNSON
 Statistics, Normal Distribution, Standard Deviation, Midwest school

Click to edit the document details