"johnT" wrote...
can countif criteria be based on 2 or more sets of data??
such as: =COUNTIF(A1:A8,"=AND(a,b)")

No. If you really mean *AND*, and the 'a' and 'b' would be things the cells
in A1:A8 could equal, then if a < b, this COUNTIF would always necessarily
equal zero. If a = b, then no point to including b.

On the other hand, if 'a' and 'b' are just tokens for different conditions,
e.g., 'a' = greater than 10, and 'b' = odd integer, then you'd need to use
SUMPRODUCT, as in

=SUMPRODUCT(--(A1:A810),--(MOD(A1:A8,2)=1))