I am having trouble getting the mean and standeard deviation. could you please show me how ? thanks

perscription data

0.4-1.1

1.2-1.9

2.0-2.7

2,8-3.5

3.6-4.3

Frequency

2

2

4

3

9

Results 1 to 4 of 4

- Feb 5th 2008, 03:34 PM #1

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- Feb 5th 2008, 03:54 PM #2

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whats wrong?

the mean is the sum of the mid points of each class times the class frequency divided by the total frequency

and then the standard deviation is $\displaystyle \sqrt { \frac { \sum{fx^2}}{\sum{f}} - \mu^2 } $

its just a simple formula where are you having trouble ?

- Feb 5th 2008, 04:25 PM #3

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- Feb 5th 2008, 04:43 PM #4

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