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202 bytes added ,  23:53, January 18, 2009
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The '''expectation''' of random variable <math>X</math> with probability density function
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The '''expectation''' of continuously distributed variable <math>X</math> with [[probability density function]]
 
<math>f(x)</math> is
 
<math>f(x)</math> is
 
:<math>
 
:<math>
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f(x)dx.
 
f(x)dx.
 
</math>
 
</math>
This is also the [[mean]] of random variable <math>X</math>.
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For a discretely distributed variable <math>X</math> with [[probability mass function]]
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<math>p_{k}</math> it is
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:<math>
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\mbox{E}[X] =  \sum_{k} p_{k}x_{k} 
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</math>
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The expectation is also the [[mean]] of random variable <math>X</math>.
    
The expectation with respect to some function <math>g(X)</math> is
 
The expectation with respect to some function <math>g(X)</math> is
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