statistical error

[NMDC]

dear all,

Please can anyone explain why the statistical error result from the statistic report is different when i calculate it manually?

e.g this is the result from rockworks report:

Mean .................................... 2.68

Standard Deviation ...................... 2.91

Standard Deviation Error ................ 0.75

when i calculated manually using the formula

SE = StandDev./Sqrt of mean (Where mean is 2.68) =

1.777565

meanwhile in both instances the mean and standard deviation were the same.

Thanks.

[NMDC]

thanks tom i found the solution to the above rockworks considers n as population size.