Measuring the quality of an e learning project

Hi Friends,

I am about to set up an e learning QA process for the new company that i have joined in.

My managers want to have a means (like a percentage or any other way) to measure the quality of the e learning course to report to the clients.

I can figure out the defects or edits in a course. But am not sure how to arrive at a way to find the defect percentage or quality percentage in a course.

If there are any ways that you guys may have come across, please share it with me.

Thanks in advance.

Kiran