how do you average time

[nielson]

Hi ,

I need to find the average time it takes students to take exams . I use the following formula =text(end time - start time, "h:mm"). I am able to calculate the amount of time it takes a student to take the exam. Now I need a formula to calculate the average time students take to complete a test. I have over 80 times i need to average. Whenever i try a formula I keep getting 0. Please help

Nielson

 

[Prosperina]

What if the times occur on different dates? How do I get the time averages ignoring the dates?