stdev calculation error

[Jon Spink]

Create a table with one currency field and enter two
records, e.g. 400 , 1000.
1. Create a query to return the standard deviation of the
two numbers using the 'stdev' SQL function. (=424.26406871)
2. Now call up the first query twice in another query and
display the standard deviation (once) again.
(=1077.0329614)

My results show that in 2. the calculation of the stdev
assumes the mean is zero.

 

[Michel Walsh]

Hi,


have you the SQL statement you used at step 2?


Vanderghast, Access MVP

 

[Jon Spink]

yes:

SELECT Data2Sdev.SDev
FROM Data2Sdev, Data2Sdev AS Data2Sdev_1;

and the SQL for 'Data2Sdev' is:
SELECT StDev([Data2].[Sum1]) AS SDev
FROM Data2;

 

[Michel Walsh]

Hi,


Reproducible here. Note the problem does not occur with Double, but
occur with Currency (as you mentionned) and is even stranger with Decimal.


I report the problem to Microsoft, as I suggest you do too (if you have
any free report incident left).



Vanderghast, Access MVP

yes:

SELECT Data2Sdev.SDev
FROM Data2Sdev, Data2Sdev AS Data2Sdev_1;

and the SQL for 'Data2Sdev' is:
SELECT StDev([Data2].[Sum1]) AS SDev
FROM Data2;

-----Original Message-----
Hi,


have you the SQL statement you used at step 2?


Vanderghast, Access MVP





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