Hi
for an explanation see:
http://cpearson.com/excel/rounding.htm

As solution use
=ROUND(STDEV(...),2)

"Non-zero return for Stdev" wrote:

Hi,

I get some non-zero results when using Microsoft Excel 97 to caluclate
Standard Deviation for the following numbers having the same set of numbers:

1) 4.8, 4.8, 4.8 = Stdev(4.8,4.8,4.8) = 8.43E-08
2) 0.71, 0.71, 0.71 =Stdev(0.71,0.71,0.71) =1.05E-08
3) 0.815, 0.815, 0.815 = dtdev(0.815,0.815,0.815) =1.05E-08

Theoretically, for same set of numbers, the Std deviation should be 0 but
when using the Excel to compute Stdev, I discover this is not true for all
the numbers (eg see above).

Any solution to ensure that when using the Excel to compute Stdev for the
set with all same numbers will always return a zero?

Regards