The chart in the attachment seems to be based on the percentages of the five categories. Since percentages should add to 100% the expected average would be 20%, which is what the following formula (pasted into cell L6 and dragged over and down to N20) yields:
Formula: copy to clipboard 
=IF(H6="",NA(),AVERAGE(H$6:H$20))

Let us know if you have any questions.