OCRMathsExam Board Revision

OCR Maths Probability Revision Notes

Master OCR Maths Probability using simple revision notes, key facts and practice questions — all generated by AI for your exam.

Probability is a measure of how likely an event is to occur, expressed as a number between 0 and 1. Understanding probability is essential for making informed decisions based on uncertain outcomes.

Key Concepts

  • 1Probability ranges from 0 (impossible event) to 1 (certain event).
  • 2The sum of probabilities of all possible outcomes of a random experiment equals 1.
  • 3Independent events do not affect each other's probabilities.
  • 4The probability of the complement of an event is 1 minus the probability of the event.
  • 5Conditional probability is the probability of an event given that another event has occurred.

Simple Explanation

Probability tells us how likely something is to happen. If something is certain, its probability is 1, and if it's impossible, its probability is 0. For example, flipping a coin has a probability of 0.5 for heads and 0.5 for tails. We can use probability to predict outcomes and make decisions based on chances.

Memory Trick

“Remember 'P(0-1)' to think of probability: P for Probability, 0 for impossible, and 1 for certain.”

Flashcards

Question1 / 5

What is the probability of an impossible event?

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Exam Questions

Describe and explain the concept of conditional probability. [6 marks]

6 marks
View mark scheme hint▾

Define conditional probability and provide examples, including the formula and its application.

Explain how to calculate the probability of independent events. [4 marks]

4 marks
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Define independent events and provide the multiplication rule with an example.

What is meant by the complement of an event? [2 marks]

2 marks
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Define complement and relate it to the probability of an event.

Practice Quiz

Question 1 of 5Score: 0

What is the probability of rolling a 3 on a fair six-sided die?

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