PGCET2010-CS

Question

The expected value of a probability function, when probability is measured on a scale of 0 to 1, coincides  with it's

(a) Mean

(b) Variance

(c) Standard deviation

(d) None of them

Comments

expected value and mean both are same (mostly). So, I think answer should be (a) and term 'expectation' is used for random variables, not for probability function..

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@ankitgupta.1729

why not s.d.?

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mam, expectation gives weighted sum. Suppose, you have sample input as $1,1,1,1,3,3,5,5,5$ then expected value will be $1*\frac{4}{8} + 3*\frac{2}{8} + 5*\frac{3}{8}$   which is also a mean.

Now, Suppose, random variable is $X$ Then

Standard Deviation(X) = $\sqrt{Var(X)}$ = $\sqrt{E(X^{2})-[E(X)]^{2}}$ which is not equal to E(X) or mean generally.

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when probability is measured on a scale of 0 to 1, coincides  with it's....... i'm not understanding what it means .....