Showing posts with label Expected Value. Show all posts
Showing posts with label Expected Value. Show all posts

Tuesday, February 12, 2013

Definition of Expected Value

Definition of expected value:
Expected value learning is one of the most essential concepts in probability. The expected value of a real-respected random variable gives the center of the distribution of the variable, in a special sense.

The expected value may be naturally understood by the law of large numbers: The expected value, when it exists, is almost for sure the limit of the sample mean as sample size grows to infinity.

The term "expected value" can be misleading. It must not be a confused with the "most probable value." The expected value is in a general not typical value that the random variable can take on. It is an often helpful to the interpret the expected value of a random variable as the long-run average value of the variable over many independent repetitions of an experiment. Is this topic Expected Value of Uniform Distribution hard for you? Watch out for my coming posts.


Definition of expected value:

The Definition Expected value (EV):

The expected value is the best prediction of an variable's value, and is the computed by multiplying each outcome by the probability of its occurrence and then averaging them.

The calculated value of a variable quantity which is most likely to occur. If a variable x can take any of the values (x1,x2,…..,xn) with corresponding probabilities (p1,p2,.......,pn) then expected value x or expectation of x is written as E(x)=p1x1+p2x2+…….+pnxn.

The general format of the Expected value is

definition,the Expected Value = Number of problem x Particular probability.

Formula for  expection for function f(x):

E[ f(X) ] = S f(x)P(X = x)

I have recently faced lot of problem while learning Definition of a Rational Number, But thank to online resources of math which helped me to learn myself easily on net.


Definition of Expected value : properties and example problems:


Properties of expected value:

The following properties are used to find the expected value. These properties are shows to the real respected random variable that gives the expected value.from definition

1. Show that E(X + Y) = E(X) + E(Y)

2. Show that E (cX) = cE(X)

3. Show that if X 0 then E(X) 0.

4. Show that if X Y then E(X) E(Y

5. Show that |E(X)| E (|X|)

The above five properties are mainly used in solving a problem of expected value.

Expected values Example:

The Experiment is to rotate a standard roulette wheel, and put money on the table minimum, ten dollars, on red.  Let X is my profit in dollars. X has two possible outcomes:  +20 and –20.  Since there are 18 red numbers out of 68 numbers on the wheel, we have P(X = +20) = 18/68, and P(X = –20) = 40/68.

Sol:

So we have, expection formula for function f(x)

E[ f(X) ] = S f(x)P(X = x)

E(X) = (20) (18/68) + (-20) (40/68) = 5.294-11.764 = - 6.47

On average, I lose a bit over fifty cents every time I place the minimum bet on red.