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Expectation (math)
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Revision as of 23:53, January 18, 2009
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23:53, January 18, 2009
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The '''expectation''' of
random
variable <math>X</math> with probability density function
+
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>.
+
+
For a discretely distributed variable <math>X</math> with [[probability mass function]]
+
<math>p_{k}</math> it is
+
:<math>
+
\mbox{E}[X] = \sum_{k} p_{k}x_{k}
+
</math>
+
+
+
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
Qwestor
127
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