If X-N(u,v) show that E((X-u)^3)=0. Hint: use symmetry.

Printable View

- October 15th 2011, 05:34 AMDukeexpected value
If X-N(u,v) show that E((X-u)^3)=0. Hint: use symmetry.

- October 15th 2011, 06:27 AMCaptainBlackRe: expected value
- October 15th 2011, 06:30 AMCaptainBlackRe: expected value
- October 15th 2011, 06:32 AMTKHunnyRe: expected value
1) Where did you use symmetry?

2) Are you SURE ? - October 15th 2011, 07:10 AMDukeRe: expected value
- October 15th 2011, 07:17 AMTKHunnyRe: expected value
Oh, so IF . That might be related to Symmetry.

As for , think really hard about the "Parity" that CaptainBlack is talking about. We know already that . Hmmm... More Symmetry? - October 15th 2011, 07:29 AMDukeRe: expected value
E(X) is not 0. E(X)=u. I thought parity referered to odd and even

- October 15th 2011, 08:08 AMTKHunnyRe: expected value
...and since we don't care about X, but , we did get somewhere.

"Parity" has other meanings.

In this case, if you cube a negative number, what do you get? Positive or Negative?

If you cube two numbers, does their relationship change? In other words, if a > b, for a, b > 0, what can we say about a^3 vs. b^3? Same or different? - October 15th 2011, 11:19 AMCaptainBlackRe: expected value
- October 15th 2011, 11:23 AMCaptainBlackRe: expected value
This thread is going nowhere because you are not taking much notice of what people are telling you, now:

Go back to post #3 Where you were told that

and that

Now write out as an integral and post what you get here.

As a further hint you will find the definition of the expectation of a function of a continuous RV in Definition 1 >>here<<

CB - October 15th 2011, 11:41 AMDukeRe: expected value
The link suggest I integrate Y^3 * pdf which from wikipedia is some horrible function.

- October 15th 2011, 11:47 AMCaptainBlackRe: expected value
- October 15th 2011, 12:03 PMDukeRe: expected value
how does this help?

- October 15th 2011, 12:24 PMCaptainBlackRe: expected value
- October 15th 2011, 01:01 PMSpringFan25Re: Show that question
**edit:**removed, for some reason i didn't notice the earlier 10 replies on the thread, if anyone used my answer i think there was a sloppy change in my definition of f(x), be warned..