Problem:
The following Array formula was designed to calculate the average difference between each pair of values in columns A & B (providing both cells are not empty):
{=AVERAGE(IF(AND(ISNUMBER(A1:B5),ISNUMBER(A1:B5)),A1:A5-B1:B5))}
However, an incorrect result of "0" is returned.
Solution:
Use the AVERAGE, IF, and ISNUMBER functions as shown in the following Array formula:
{=AVERAGE(IF(ISNUMBER(A1:A5)*ISNUMBER(B1:B5),A1:A5-B1:B5))}
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