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490 bytes added ,  02:17, August 31, 2009
not "random" or "variable"
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A '''random variable''' is a [[function]] that assigns a unique numerical value to every possible event having an outcome dependent on chance.  The random variable will typically be different for each new event, such as a new toss of a coin.
 
A '''random variable''' is a [[function]] that assigns a unique numerical value to every possible event having an outcome dependent on chance.  The random variable will typically be different for each new event, such as a new toss of a coin.
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There are discrete and continuous random variables.  An example of a discrete random variable is the umber of heads observed in the ten tosses of a coin.  This random variable can only have the values 0, 1, 2, ... or 10.  An example of a continuous random variable is the mileage on your car until it breaks down.  It can have any positive value.
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There are discrete and continuous random variables.  An example of a discrete random variable is the number of heads observed in the ten tosses of a coin.  This random variable can only have the values 0, 1, 2, ... or 10.  An example of a continuous random variable is the mileage on your car until it breaks down.  It can have any positive value.
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The terminology "random variable" has been criticized as being neither "random" nor "variable".  A random variable really consists of a sampling from a certain probability distribution.  It is not purely "random" because it is limited by the predefined probability distribution (e.g., "heads" or "tails" in the case of a coin toss, with a likelihood of each determined by the likelihood of each side appearing); it is not a "variable" because it is a sample value from that distribution.
    
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== Sources ==
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