GlossariesGCSE GlossariesGCSE Maths GlossaryConditional probability

Conditional probability - GCSE Maths Definition

Reviewed by: Dan Finlay

Last updated

Conditional probability is a concept in probability theory that describes the likelihood of an event occurring, given that another event has already happened. In simpler terms, it helps us determine the probability of one event under the condition that we know another event has occurred. For example, if we want to find the probability of picking a red ball from a bag, knowing that a ball has already been picked and it was not blue, we would use conditional probability. It is an essential part of the GCSE Maths course, as it helps students understand how probabilities can change based on given conditions, usually represented by the formula

P open parentheses A space g i v e n space B close parentheses equals fraction numerator P open parentheses A space a n d space B close parentheses over denominator P open parentheses B close parentheses end fraction

where P left parenthesis A ∣ B right parenthesisis the probability of event A occurring given that event B has occurred.

Examiner-written GCSE Maths revision resources that improve your grades 2x

  • Written by expert teachers and examiners
  • Aligned to exam specifications
  • Everything you need to know, and nothing you don’t
GCSE Maths revision resources

Share this article

Dan Finlay

Reviewer: Dan Finlay

Expertise: Maths Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.

The examiner written revision resources that improve your grades 2x.

Join now