Std deviation and confidence liimts

[vipersmind]

I am trying to return a confidence interval for a population mean and am having touble writing it into my report as a calculated field.
please help....going insane

 

[pdx_man]

How do you have the function defined? Have you written the code in VBA in a Module in Access? Is the function working on it's own outside of the Query? Are you using the canned Access StDev? Just need a little more info.