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Four Types of Probability

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Explain in detail and give an original example of the four types of probability.

1) Marginal probability
2) Union probability
3) Joint probability
4) Conditional probability

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Solution Preview

All of these involve probabilities of two (or more) variables or events. The two variables (let's call them x and y) can be independent or not.

1) Marginal probability P(x)

This is the probability of x, over all possible y's. If x is some event, you would find it by dividing the number of times x occurred by the total number of observations. You wouldn't consider what y did during that same time.

2) Union probability P(x or y)

This is the probability that either x or y or both will occur. If x and y are events A and B, then the union probability is the sum of the two events minus the joint probability:

P(A or B) = P(A) + ...

Solution Summary

Four types of probability are examined. The marginal, union, joint and conditional probability is analyzed.