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.

---

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 )

---

Etymology

Origin of conditional probability

First recorded in 1960–65

Example Sentences

Because this is a conditional probability, we restrict the sample space to consider only those outcomes that have a blue marble in the first draw.

From Textbooks • Mar. 27, 2020

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

Write your answer as a conditional probability statement.

From Textbooks • Sep. 19, 2013

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

The probability of red on the next spin is 18/38, the same as the conditional probability of red on the next spin given that there have been five consecutive reds.

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