AVERAGEIF:
Returns the average (arithmetic mean) of all the cells in a range that meet a given criteria
The AVERAGEIF function returns the average (arithmetic mean) of all the cells in a range that meet a given criteria.
Using the AVERAGEIF function:
The arguments for the AVERAGEIF function are:
Argument

Required?

Description

range 
Required 
One or more cells to average, including numbers or names, arrays, or references that contain numbers. 
criteria 
Required 
The criteria in the form of a number, expression, cell reference, or text that defines which cells are averaged. 
average_range 
Optional 
The actual set of cells to average. If omitted, range is used. 
• Cells in range that contain TRUE or FALSE are ignored. 
• If a cell in average_range is an empty cell, AVERAGEIF ignores it. 
• If range is blank or a text value, AVERAGEIF returns the #DIV0! error value. 
• If a cell in criteria is empty, AVERAGEIF treats it as a 0 value. 
• If no cells in the range meet the criteria, AVERAGEIF returns the #DIV0! error value. 
• You can use the wildcard characters, question mark (?) and asterisk (*), in criteria. A question mark
matches any single character; an asterisk matches any sequence of characters. If you want to find an actual question mark or asterisk, type
a tilde (~) before the character. 
• average_range does not have to be the same size and shape as range. The actual cells that are averaged are determined
by using the top, left cell in average_range as the beginning cell, and then including cells that correspond in size and shape to range. For example: 

The AVERAGEIF function returns the average (arithmetic mean) of all the cells in a range that meet a given criteria.