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STD function not accurate
Posted by: Y B
Date: April 02, 2016 03:09PM

Hi All,
The std function is very useful and I use it often. However, I noticed I am getting slightly different results compared to computing the standard deviation in R or Excel for the same values.

Here is my query:
select distinct stain, cell, organ, group_concat(value), avg(value), std(value) from mydata where bacteria="germ free" group by stain, cell, organ

Now here are the values from one row, from the group_concat field:

The mean is computed correctly and is: 17.68125001
The std is computed as: 7.260140888

However, when using these values in R or Excel, the std is: 7.376311

This seems like a big difference. Can anyone provide an explanation? I have been using the STD function for a while and now getting worried.


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STD function not accurate
April 02, 2016 03:09PM
April 02, 2016 08:23PM

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