Hi Ken, I did it with a calculator years ago, then later checked my work at Dartmouth on a timeshare computer (wished I had a laptop then). I would do it in steps and not try a single query. Or, I would consider using  a recordset.

Here is Chat's 2 cents worth:  There are two common formulas, depending on whether you're calculating the standard deviation of a population or a sample.

Population standard deviation
\(\sigma = \sqrt{\frac{1}{N}\sum_{i=1}^{N}(x_i-\mu)^2}\)
The points have mean  = 5 and  = 1.5.


Drag points
Give feedback
$$ \boxed{\sigma=\sqrt{\frac{\sum_{i=1}^{N}(x_i-\mu)^2}{N}}} $$

Where:

= population standard deviation
x = each individual value
= population mean
N = number of values
= add them all together
Sample standard deviation
$$ \boxed{s=\sqrt{\frac{\sum_{i=1}^{n}(x_i-\bar{x})^2}{n-1}}} $$

The important difference is that a sample uses n - 1 in the denominator, while a population uses N.

In plain English:

Find the mean.
Subtract the mean from each value.
Square each difference.
Add the squared differences.
Divide by N (population) or n-1 (sample).
Take the square root.

HTH John

Kenneth   You can use Excel functions in Access by referencing Excel in VBA.  The code below lets Access VBA use Excel's STDEV function.  Put this code in a custom function (such as MyStdDev below), and use this custom function in your query or other VBA code.  This technique is called automation.  Richard must have courses for it somewhere.  The immediate window below shows that it runs successfully.  The STDEV() function takes a range of cells in Excel, which is equivalent to an array in VBA.

If you are wondering whether you can use this function on a whole column of data in a query, like what Sum() or Count() does, the answer is unfortunately no, you cannot.  This is because you cannot create custom aggregate functions in VBA.  You must retrieve data from all rows, store them in an array, then feed the array to the function as shown below.

Kevin, you must be a mind reader. Using Excel functions in Access VBA has been on my developer to-do list for a while now.

I've covered quite a bit of Excel automation, such as using Access to create spreadsheets. I used it myself for pulling stock portfolio data, but I haven't yet covered tapping into Excel's function library like this. I've got a couple of other topics to cover first, but this is definitely coming up after that.

SQL Server also has a STDEV function, if the user doesn't have Excel on their PC.  But automation is still useful in many situations.  

P.S.  "Automation," coined in the 90s, is an unfortunate word because it sounds like AI today.  But it's just a coding technique, and has nothing to do with AI.

Yeah, I think of automation more as issuing commands to another program and having it do work in that program. With Excel, for example, Access can create a new workbook, put values in worksheet cells, call Excel functions, format the sheet, and save the finished file. Access is basically telling Excel what to do rather than just borrowing one of Excel's tools.

I do the same thing with Word. My handbook generator gathers the data in Access, then issues automation commands to Word to build the final document, insert pictures, set fonts, and so on. That's what I consider automation.

I will talk about this in the next Quick Queries video: https://599cd.com/QQ

I know how to figure out STDEV in Excel, I just wanted to knowif I could formulate right in Access.  I will continue using Excel.  Thank you. Go Bills