what is the expected value of x^2 in mathematical form?

Question

anonymous · Answer

in a simplified form

lgbasallote · Answer

what do you mean?

parthkohli · Answer

$x \times x$ I think that's what you mean.

anonymous · Answer

yeah

lgbasallote · Answer

mathematical form?

parthkohli · Answer

Hmm. Similarly:

$ \color{Black}{\Rightarrow x^3 = x \times x\times x}$
$ \color{Black}{\Rightarrow x^4 = x \times x \times x \times x}$

parthkohli · Answer

'Mathematical form' is still ambiguous.

anonymous · Answer

some stats people know may know

unklerhaukus · Answer

$$\langle x^2\rangle =\sum\limits_{j=0}^\infty x^2 P(j)$$

parthkohli · Answer

lol

lgbasallote · Answer

$$\int 2xdx$$

anonymous · Answer

this reminds me of a very fundamental/basic question in calculus..please see my next question..i'll post link..

lgbasallote · Answer

$$\frac{d}{dx} (\frac{x^3}{3})$$

unklerhaukus · Answer

what are you doing at @lgbasallote ,

lgbasallote · Answer

$$x^2 = r^2 - y^2$$

lgbasallote · Answer

trying to get all that's x^2 and see if anythign suits him

anonymous · Answer

http://openstudy.com/study?login#/updates/4ffffc85e4b0848ddd64e880

unklerhaukus · Answer

im pretty sure i have provided the answer to the question

lgbasallote · Answer

we all think that...

unklerhaukus · Answer

,oh

anonymous · Answer

i need E(x^2)=?

unklerhaukus · Answer

the expectiation value of $x$ $$\langle x\rangle =E(x)$$

anonymous · Answer

@UnkleRhaukus yes but x^2

lalaly · Answer

$$Var(x)=E(x^2)-(E(x))^2$$

anonymous · Answer

i got the ans... thanks all

unklerhaukus · Answer

$$\sigma_x=\langle x^2\rangle-\langle x\rangle ^2$$

lalaly · Answer

:D

anonymous · Answer

ya ur right

unklerhaukus · Answer

The expectation value , or expect value of a function
is $$\langle f(x)\rangle =\sum\limits_{x=0}^\infty f(x)P(x)$$
where $P(x)$ is the probability of x

anonymous · Answer

yes for a discrete random variable

unklerhaukus · Answer

im not sure why i put j instead of x,

unklerhaukus · Answer

oh, you want a continuous function?

anonymous · Answer

no i know

anonymous · Answer

thank you

unklerhaukus · Answer

$$\langle f(x)\rangle=\int\limits_{-\infty}^\infty f(x)\rho(x)\text dx$$

anonymous · Answer

ya

unklerhaukus · Answer

where $\rho(x)$ is the probability density

unklerhaukus · Answer

so
$$\langle x^2\rangle=\int\limits_{-\infty}^\infty x^2\rho(x)\text dx$$

anonymous · Answer

@UnkleRhaukus small question the E(constant) is a constant right

unklerhaukus · Answer

if the distribution of the variable $x$  is constant , yes

anonymous · Answer

thanks