conditional probability

American  

noun

1. Statistics, Mathematics. the probability that an event will occur under the condition that another event occurs first: equal to the probability that both will occur divided by the probability that the first will occur.

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conditional probability British  

noun

1. statistics the probability of one event, A, occurring given that another, B, is already known to have occurred: written P ( A|B ) and equal to P ( A and B )| P ( B )

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Etymology

Origin of conditional probability

First recorded in 1960–65

Example Sentences

The second method is to test if the conditional probability of A given B is equal to the probability of A. Again for simplicity, we can use an already calculated value from above.

From Textbooks • Nov. 29, 2017

In order to solve Example 3.30 we had to draw upon the concept of conditional probability from the previous section.

From Textbooks • Nov. 29, 2017

The probability of picking the three of diamonds is called a conditional probability because it is conditioned on what was picked first.

From Textbooks • Nov. 29, 2017

Either C would be pardoned or himself, so by all the laws of conditional probability, his chances of survival had gone up from 1/3 to 1/2.

From Scientific American • Apr. 15, 2011

Before I get to a serious application, I’d like to mention another con game which works because of confusion about conditional probability.

From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos