STDEV with multiple conditions

Hello and welcome to the forum.

With arrays, AND is written by multiplying two arrays together (and add for OR).

Since I don't have a sample sheet in front of me, all that I can do is correct the syntax for your formula. That is:

=STDEV.S(IF((DataSheet!$S:$S=Statistics!A3)*(DataSheet!$AT:$AT=Statistics!B3),DataSheet!$BC:$BC)) Ctrl Shift Enter

Since this is an array formula, you will want to limit your ranges instead of using whole column references (i.e. change $S:$S to something like $S$2:$S$1000).

Ah, yes- totally a syntax problem.

Thank you, best regards