AVG returns the average (arithmetic mean) of the specified cell range

AVG(Cell Range):

Cell Range:  The cell range to anaylze. i.e. (A1:A31) 

NOTES:

The AVG function handles data qualifers with default rules of:

< are treated as zeros (<2 = 0, <100 = 0)
> are treated as entered value (>4 = 4, >1000 = 1000)
ND are treated as zeros

If you need to specify different rules for data qualifiers use GAVGZ or STATZ. 

The AVG function takes the average of the displayed values in the cell, use AVERAGE to use the values in the cell.  Example, if you have two cells, one is equal to 22/7 (3.14159...)  and displayed to zero decimal places (i.e. 3) and the second cell is equal to 1.  AVG will take the average of 3 and 1 and return exactly 2.0000 whereas AVERAGE will take the average of 3.14159 and 1 and return 2.0714... 

EXAMPLES:

AVG(C4:C22)