Trying to put a formula that will compute the average rating based on organizational grouping.
I have a smartsheet that has a drop down field which includes organization functions like: engineering, IT, Sales, Marketing, ...
I have another field that is a numeric rating for these organizational functions.  1 thru 5. 
I need a report that will aggregate and display by organization and their corresponding average ratings.  Something like
Organization                    Average Rating
Engineering                     5
Sales                               4.5
IT                                     3
...
I know how to use Sights dashboard to display the results, but need help in putting the formula(s) together.  Thanks in advance for any help