Average Standard deviation calculated per month

[BobKoenen]

Hi I want to calculate a montly standard deviation 

I want to calculate the standard devation in DAX from my fact table but not the SD per row but totalled per month. 
My data looks like this 

Customer	date	Sales
A	1-1-2023	20
A	15-1-2023	50
A	5-2-2023	10
A	10-3-2023	150
B	1-1-2023	50
B	5-3-2023	1

Now I want a DAx formula which first calculates the total sales per month. e.g. for customer A see below and after that calculates the standard deviation per month. 

Customer	Month	Sales
A	1-2023	70
A	2-2023	10
A	3-2023	150

If i would calculate the st dev using 

STDEV.P(Tabel[Sales])  this gives me 57.35 which is correct. How can i build this logic in to a dax formula

hope you can help me

[eliasayyy]

if you want the sum of sales for each month alone, try using 

SUMX(values([Month-Year]),[sales measure])

or

CALCULATE(SUM([Amount]),ALLEXCEPT(Table,[Month-Year],[Category]))

this will give you sum of sales by month - year use the first if you dont have ctageories an dsub categories and use the second if you have categories and sub categories

[some_bih]

Hi @BobKoenen try measure 

STDEVX.P(Sheet29,Sheet29[Sales])

Sheet29 adjust to your table name

Connect date column with Date table and check results. You provided sample of data so it is hard to check if it is ok. I hope this help