sumif function

[Guest]

Hello -
I have a range of names in column A and a range of ages in column B. How
can I determine the average age per unique name?

 

[Guest]

Use this formula in C1 and copy down to bottom of your range
=SUMPRODUCT(--($A$1:$A$1000=A1),--($B$1:$B$1000))/SUMPRODUCT(--($A$1:$A$1000=A1),--($B$1:$B$1000<>""))

 

[Aladin Akyurek]

=AVERAGE(IF(NameRange=Name,AgeRange))

which must be confirmed with control+shift+enter, not just with enter.
Note also that this type of formulas do not admit whole column refernces
like A:A as range.