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# Mean and Std deviation on a varying data set in an Access form.

## Mean and Std deviation on a varying data set in an Access form.

(OP)
thread702-1136748: Calculate Standard Deviation in Form Send Value to Table

Like the above thread I need to get a std deviataion of a data set on a form.
However, my issue is that my data set could be between 3 and 10 of the circled items.
The remaining 7, 6, 5, 4 fields could be blank.
How do I write this in the macro so it does't throw an error?

The calcs for each of the data sets are;
Av Density (this ones obvious)
Characteristic Voids CV= Avg x + (k*stddev x)
Characteristic Density Ratio CV= Avg x - (k*stddev x)

Have attached a pic to show the common data sets.

Any help on this would be appreciated.
I've had a lot of fun with Access over the years, but this one is getting me.

### RE: Mean and Std deviation on a varying data set in an Access form.

(OP)
Managed to get my code working

I'd like to share how I did this

Be mindful that x was a varying number of fields from 3 to 6.
x was stated as number of samples on my form.
"x = Forms![Density Test]![No of Test]"
So had to be able to calculate from whatever number of fields was required.

'Average Density Ratio
For q = 1 To x
Dat4 = Choose(q, Forms![Density Test]!DR1, Forms![Density Test]!DR2, Forms![Density Test]!DR3, Forms![Density Test]!DR4, Forms![Density Test]!DR5, Forms![Density Test]!DR6)
S4 = S4 + Dat4
Next
Forms![Density Test]!MDR = S4 / x
MDR = S4 / x

'Charact Density Ratio
For t = 1 To x
Dat5 = Choose(t, Forms![Density Test]!DR1, Forms![Density Test]!DR2, Forms![Density Test]!DR3, Forms![Density Test]!DR4, Forms![Density Test]!DR5, Forms![Density Test]!DR6)
S5 = S5 + (Dat5 - MDR) ^ 2
Next
DRSD = Sqr(S5 / (x - 1))
Forms![Density Test]!CDR = MDR - (Forms![Density Test]!K * DRSD)

K is a factor of risk applied to the std dev. THe base calc is Characteristic DR = Av DR-(0.92*stddev of DR)
The density ratios are across 6 different fields in a table and on a form.

Thanks for the help here on this site.
Really appreciated!

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