# Difference between an expectation value and an average

1. ### Scott4775

9
Hi everyone,

What is the difference between an expectation value and an average. I may have this wrong, but is it something along these lines:

You perform a series of measurements on a given observable, such as momentum, and the average value of all these measurements is your expectation value?

I'm sorry if I have this concept totally wrong. I appreciate any help you all may have.

Thanks!

### Staff: Mentor

The expectation value is the average that you expect to get, calculated from the wave function. As you take more and more measurements of the same quantity, their average tends closer and closer to the expectation value. In the limit as the number of measurements goes to infinity, we expect the measured average to become equal to the expectation value.

3. ### Scott4775

9
Thank you, that explains it perfectly! :)