Biff wrote...
Try this:

Entered as an array using the key combination of CTRL,SHIFT,ENTER:

=AVERAGE(IF(A1:A20<0,A1:A20))
....

As I never tire of pointing out, better to use

=AVERAGE(IF(rng0,rng))

because if values could be negative as well as positive, then
legitimate values could also be zero, so the only time it make sense
(mathematically) to exclude zeros is when all values should be only
positive or only negative.