# Thread: probability and expected value

1. A have a question whre the random variables x and y have the following joint probability density:

I resolve the constant a = 6/5, so ,

What the expected value of 1 / X, given that Y = 3/2.?

tks

2.

3. Your notation is confusing. What is "se"? You should not use the same letters for random variables and function argument.

4. Hi Mathman,

Sorry, "se" = "for".

tks

5. I get a = 1/2. Could you show me your derivation?

6. We can say that??

So,

a=6/5 (?)

7. Also check your boundary conditions, the original density function was from 0 to 2 but you are integrating from 1 to 2?

8. Dear river_rat and mathman,

Sorry, the original question is from 1 to 2 and not 0 to 2 as:

9. Ok, given that I get ?

10. Hi river_rat

My development gave my 6/5 (see post of 11 nov). Something wrong in my reasoning?

11. The bounds on the inner integral look wrong, remember that Y >= X

12. a=3/2

right?

13. That looks good

Have you calculated the conditional expectation yet?

14. Not yet... today. Tks!!

15. 18/10?

16. Now have 2 other topics to resolve:

(b)Define the marginal probability density function py (Y).

(c) Determine o valor esperado de 1/X, dado que Y = 3/2.