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Probability

What is a probability distribution?

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September 13, 2011 2:21PM

A probability distribution is a function that describes the probability of obtaining a certain outcome where the outcomes are not equally likely. There is a fixed probability of getting each outcome, but the probabilities are not necessarily equal. For example, roll 2 dice, there are 36 equally likely outcomes with a probability of each occurring being 1/36. However if we look at the sum of the numbers, there is only one outcome that gives a sum of 2 (1&1) , so P(sum 2) = 1/36, but six outcomes that give the sum of 7 (1&6, 2&5, 3&4, 4&3, 5&2, 6&1), so P(sum 7) = 6/36 = 1/6.

Probability distributions can be tabulated, or there are functions that can be used to calculate the probabilities of getting each outcome.

A probability distribution is a function that describes the probability of obtaining a certain outcome where the outcomes are not equally likely. There is a fixed probability of getting each outcome, but the probabilities are not necessarily equal. For example, roll 2 dice, there are 36 equally likely outcomes with a probability of each occurring being 1/36. However if we look at the sum of the numbers, there is only one outcome that gives a sum of 2 (1&1) , so P(sum 2) = 1/36, but six outcomes that give the sum of 7 (1&6, 2&5, 3&4, 4&3, 5&2, 6&1), so P(sum 7) = 6/36 = 1/6.

Probability distributions can be tabulated, or there are functions that can be used to calculate the probabilities of getting each outcome.