You are Here: Home >< Maths

# Expectations (over variables and conditional) watch

1. Say we have Ex(f)
Where f is a function of random variables
I'm not too sure what the subscript X means.

If f only contains x, say f=1/X
Is Ex(1/X) the same as E(1/X)?

OR Ex(ZX)?

Similarly for conditional expectations:
Is E(f(X)|X) the same as E(f(X))
2. (Original post by DQd)
Say we have Ex(f)
Where f is a function of random variables
I'm not too sure what the subscript X means.

If f only contains x, say f=1/X
Is Ex(1/X) the same as E(1/X)?

OR Ex(ZX)?

Similarly for conditional expectations:
Is E(f(X)|X) the same as E(f(X))
The one thing I would say is that subscripts should usually be defined in a self contained way, I.e. Wherever you have seen Esubscriptx, it should have been defined somewhere most likely in your notes.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 22, 2017
Today on TSR

### Congratulations to Harry and Meghan!

But did you bother to watch?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams