Standard Deviation

[tombo10]

I'm trying to get an Access report to calculate the standard deviation of a set of numbers. For this example the numbers are 63.50, 63.51, 63.51, 63.48, 63.49, 63.49, 63.49, 63.49, 63.49. When I do this in Excel the Stdev is 0.010138. But the Access report calculates it as 0.005744. My end goal is to calculate Cp & Cpk on the report but these false Access numbers makes it impossible. Any help on why Access calculates Stdev differently than Excel?

[alansidman]

How are you calculating your Standard Deviation in Access? Are you using the Group By query as explained here:

http://www.blueclaw-db.com/accessque...e_function.htm

[tombo10]

Sorry, obviously my access skills are weak but I'll try to answer as best I can. I created a query to sort out the data I want but did no calculations in the query. Using the report wizard I set it up to sort by operation and did a summary of "inspection value" data for each operation. In the control source "expression builder" I created this: =StDev([INSP_VAL]). I did the same thing for sum, avg, min & max and they all worked fine except stdev. I realize now this might be more than I can accomplish without some programming training.

[alansidman]

When I create a group by query and use the StDev I get the following result 1.01379376317721E-02. This appears to match the Excel number you received. Here is the SQL statement I used.

SELECT StDev(Table4.Field1) AS StDevOfField1
FROM Table4;

I suggest you do all calculations in your query and then make the query your record source for your report.