Answer to Question #12177 in Statistics and Probability for jamie

Question #12177

weighted average question. people taking courses. I have the following:
% of people and #of people and their completion rate.
20% = 6 people = 72% completion rate of courses
30% = 9 people = 85% completion rate of courses
50% = 15 people = 95% completion rate
I know it is wrong to take the average of 72%, 85% 95% to get the average completion rate ...but how do i figure out the weighted average?

Expert's answer

Weighted average is calculated as a summ of products values and their weights:
W=0.2*72%+0.3*85%+0.5*95%=87.4%