Calculated Column - Standard Deviation (NOT a Measure)

Hi All,

I need to calculate the average and standard deviation over a large number of records as a calculated column.

I've created a calculated column which provides the 6 week average of sales for each day.

I need to create another column that selects the same records and provides the standard deviation. I tried to just change the average to stdev.p but that didnt work.

With those two values in hand for each transaction I will create a future supply projection for each transaction.

I have this working in a summarize statement in a calculated table but would really like to do it in a calculated column to avoid having to join the result back to the main fact table as the cardianlity of that join is the entire record set.

FutureProjection=IFERROR(NORM.INV(0.98,'Fact'[Mean],'Fact'[STDV]),0)

Mean = VAR _Date =
DATEADD ( 'FACT'[Date], -7, DAY )
RETURN
CALCULATE (
ROUNDUP(AVERAGE( 'FACT'[COLQty Sales] ),0),
ALLEXCEPT ( 'FACT', 'FACT'[Key] ),
'FACT'[Complete] = "COMPLETE",
DATESINPERIOD ('Calendar'[Date],_Date,-42,DAY))
)