Countif and averages avoid blanks

I hope someone can help me. I am relatively new to Excel and I was needing to create a workbook to track training compliance at my facility. What I have is one column each: First Name, Last Name, Supervisor, employee number, course name etc. The way I have it set up is if the user has completed the course they have a 1 in the appropriate column, if not they have a 0. Based on that I have a percentage of completion. The trouble I am having is getting a percentage of completion for the supervisor. Small illustration below:

Last Name First Name Supervisor Course1 Course2
Doe John Sup1 1 1
Doe Jane Sup2 0 0

Based on the information above one sup would be at 100% the other would be at 0%. There are 257 employees that I have to monitor with roughly 7 sups. Can anyone help? I tried to look through the forums but did not come across anything immediately that would help. Thanks

Please help people help you by editing the title of your post so someone has a clue as to what specific help you need.

Assuming Supervisors are in C2:C260 and 1s and 0s in D2:E260

then list your supervisors in G2:G8

In H2 use this formula

=AVERAGE(IF(C$2:C$260=G2,D$2:E$260))

confirmed with CTRL+SHIFT+ENTER and copied down to G8

[Note: to confirm with CTRL+SHIFT+ENTER...paste formula into cell, select that cell and press F2. Hold down CTRL and SHIFT keys and press ENTER. Curly braces like { and } will appear around the formula in the formula bar]

I just wanted to say thanks to everyone that offered suggestions. I was able to use a little bit of this and that and come up with a solution for exactly what I needed. Thanks a bunch.