How to Calculate Conditional Probability

An easy tutorial to calculate the probability of intersection of more than two events(Conditional Probability) with formula and examples.

Calculating Conditional Probability

Conditional Probability is a probability of one event occurring based on the another event (s) that has already occurred. To put it simple, we have already given the probability of event A and we need to find the probability of event B based on the event A. So the probability obtained is the conditional probability of B given A. It can be written as P(B/A). Learn here how to calculate conditional probability with simple example problem.
How To Calculate Conditional Probability
Calculating conditional probability is essential if we are calculating the probability of intersection of more than two elements.
Conditional Probability Formula:
P (A and B) = P (A) x p (B/A)
So,
P(B/A) = P (A and B) / P(A)
Conditional Probability Formula
Conditional Probability Example:
Consider that a interviewer is conducting the online aptitude and software test for a set of candidates. 45 % of people passed both the test and 65% passed the aptitude test. Find the percentage of candidates who passed the first test, also passed the second one?

Step 1:
Consider,
Aptitude test (A) = 65 %
Aptitude and Software test (A and B) = 45%
P(B|A) = ?
Conditional Probability Example
Step 2: Substitute the given values in the formula.
P(B/A) = P (A and B) / P(A)
= 45 / 65 = 0.6923 = 69 %
P (B/A) = 69%

The percentage of candidates who passed the first test, also passed the second one is 69%

Conditional Probability Calculation


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