EXPECTATION

OF A DISCRETE RANDOM VARIABLE

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Expectation (average) of discrete-valued random variable X is



Three coins example:


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Another Way to think about Expectation

Think of putting masses on a ruler. Put the mass with mass equaling the probability of the event PX(x) at the position x. The Expected Value of the random variable is the point where you should put your finger to make the masses balance. This balancing point is also called the centroid.



See SeeSaw Activities by the Calculus group in Project Links for more information on Centroids.

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RELATED
CONCEPTS

  Random Variables
Probability Mass Function
Cumulative Distribution Function
Expectation of a Continuous Random Variable
Important Discrete Random Variables
Arithmetic Mean
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