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| a random variable assumes any of several different numeric values as a result of some random event; random variables are denoted by a capital letter such as X |
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| a random variable that can take one of a finite number of distinct outcomes |
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| Continuous random variable |
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Definition
| a random variable that can take any numeric value within a range of values; range may be infinite or bounded at either or both ends |
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| the probability model is a function that associates a probability P with each value of a discrete random variable X, denoted P(X=x) or with any interval of values of a continuous random variable |
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| the expected value of a random variable is its theoretical long-run average value, the center of its model; denoted E(X), it is found (if the random variable is discrete) by summing the products of variable values and probabilities |
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| the variance of a random variable is the expected value of the squared deviation from the mean |
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Definition
| the standard deviation of a random variable describes the spread in the model, and is the square root of the variance |
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