# How to find what % of the data lies within one standard deviation of the mean

• Sep 24th 2010, 10:12 AM
-DQ-
How to find what % of the data lies within one standard deviation of the mean
DATA SET:

5.3
7.2
5.5
6.5
5.7
4.7
7.5
7.5
7.1
5.4
5.4
4.4
5.7
6.3
4.2
7.1

My work:

Mean: 5.969
St. dev: 1.090

5.969 + (1.090) = 4.879
5.969 - (1.090) = 7.059

Range: 4.879-7.059

8 of 16 values are in that range

WHERE DID I GO WRNOG?
• Sep 24th 2010, 08:59 PM
CaptainBlack
Quote:

Originally Posted by -DQ-

WHERE DID I GO WRNOG?

Why do you think you have gone wrong?

CB
• Sep 25th 2010, 10:21 AM
-DQ-
Because the answer in the book is different. :(
• Sep 25th 2010, 11:35 AM
CaptainBlack
Quote:

Originally Posted by -DQ-
Because the answer in the book is different. :(

There are two possibilities:

1. You should have used 1/n weighting in the calculation of the SD rather than 1/(n-1) (they give the same final answer when I do the calculations either way)

2. The book is wrong (what does it think the answer is?)

CB