different result in "calcualted column" and "calulated field"

[alexelix]

Hi every one, I have set up a calculated field(measure) in a pivot table to calculate standard deviation of the sample (STDEV.S) in different month's records. Surprisingly, I get right answer for all months but wrong answer for one month (Oct). To make sure, I set up a calculated column in powerpivot to calculate standard deviation on the same month's record and I got the right answer unlike the calculated field in pivot table. So, there is a discrepancy between the result I get in calculated field(pivot table) and what I get in calculated column (powerpivot) for a month. Do you all have any idea what the reason might be? Thanks.

 

[scottsen]

This is gonna be a tough one to diagnose w/o seeing the workbook I think.