Problem with STDEV

Hi austinsense and Greg_Deckler

I have the same problem

Fact (Itemkey,DateKey,Demand) Demand is Measure from source.

DimDate (DateKey,MonthNumber)

DimItem(ItemKey,ItemNumber,CompanyKey)

Now i am trying to create standard deviation but the function 'Stdev.P' is not working.

all values are as 0's

So i tried another way by calculating individual steps:

Note: All the calculations are Measures.

CounOfMonth = COUNT(DimDate[MonthNumber])

Mean = CALCULATE([CounOfMonth],ALLSELECTED(DimItem[ItemNumber]),ALLSELECTED('Fact'))

AvgDemand = DIVIDE(CALCULATE(SUM('Fact'[Demand]),ALLSELECTED('Fact'),ALLSELECTED(DimItem[ItemNumber])),[Mean],0)

Demand-AvgDemand = SUM('Fact'[Demand]) - [AvgDemand]

Sqr(Demand-Avg) = [Demand-AvgDemand]^2

Sqr(Demand-Avg)/Mean = DIVIDE([Sqr(Demand-Avg)],[Mean],0)

till here values are coming fine but not totals. and i concern about totals why because i once i remove MonthNumber from the table only one record and one total will which will be the same values.

OR Combining all above formulas into a single Measure is also coming fine, as:

StdDev = DIVIDE((CALCULATE(SUM('Fact'[Demand]),ALLSELECTED(DimItem[ItemNumber])) - DIVIDE ( SUMX (ALLSELECTED('Fact'),'Fact'[Demand]),[Mean]))^2,[Mean])

Once you add all values in Sqr(Demand-Avg)/Mean column

OR

Once you add all values in StdDev column

AND

Try try to do square root of it it is giving me the correct standard deviation as follows:

I filtered on a single item and working on it.

But when i  try to complete standard deviation formula by applying SQRT to StdDev:

StdDev = SQRT(DIVIDE((CALCULATE(SUM('Fact'[Demand]),ALLSELECTED(DimItem[ItemNumber])) - DIVIDE ( SUMX (ALLSELECTED('Fact'),'Fact'[Demand]),[Mean]))^2,[Mean]))

OR

by creating another Measure:

SQRT = SQRT(CALCULATE([Sqr(Demand-Avg)/Mean],ALLSELECTED(DimItem[ItemNumber]),ALLSELECTED('Fact')))

The results looks like this

Why my totals are not coming fine?

What did i miss?

Thanks in advance.