What It Does
This formula will take the average of a numerical range then return the count of the items in the range that are less than the average.
How It Works
AVERAGE(Numbers) will return the arithmetic mean or average of the Numbers. In our example this is (13+5+7+9+20+3+4+6)/8 = 8.4. “<"&8.4 then creates the text string “<8.4" which is used as a condition in our COUNTIF function.
COUNTIF(Numbers,”<8.4") will then count all the numbers in our list which are less than 8.4. In our example this results in 5 since there are 5 numbers in the list that are less than 8.4.