suppose cells are a1:b4 have following values

east 5
west 7
north 6
east 3

so you can do an average like =average(if(a1:a4="east",b1:b4)) and that will
equal a value of 4 -- (5+3)/2

What if you wanted to calculate the average of numbers in a1:a4 where it
equaled 2 conditions - either east or west. So that would be 5 -- (5+3+7)/3.

How would the second formula be written to average numbers where either of
two conditions are met?