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 the measure of the likelihood that an event will occur. It is expressed as a number between 0 and 1, where 0 indicates impossibility and 1 indicates certainty. Understanding probability is essential for making informed decisions based on uncertain outcomes.
Key Concepts
- 1Probability is calculated as the number of successful outcomes divided by the total number of possible outcomes.
- 2Events can be independent or dependent, affecting how probabilities are calculated.
- 3The sum of probabilities of all possible outcomes in a sample space equals 1.
- 4Complementary events are those that cover all possible outcomes, and their probabilities sum to 1.
- 5Conditional probability measures the probability of an event given that another event has occurred.
Simple Explanation
Probability helps us understand how likely something is to happen. You can think of it as a way to measure chances, like flipping a coin or rolling a dice. If you want to know how likely it is to get heads when flipping a coin, you would say there is a 50% chance, because there are two possible outcomes: heads or tails.
Memory Trick
“Remember 'P.E.A.C.E.' for Probability: P = Possible outcomes, E = Events, A = All outcomes, C = Complementary events, E = Expected outcomes.”
Flashcards
What is the probability of rolling a 4 on a fair six-sided die?
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Exam Questions
Describe and explain the concept of conditional probability. [6 marks]
6 marksView mark scheme hint▾
Define conditional probability, provide formula, explain with an example, and discuss its significance.
Explain how to calculate the probability of independent events. [4 marks]
4 marksView mark scheme hint▾
Define independent events, state the multiplication rule, and provide an example calculation.
What is meant by complementary events? [2 marks]
2 marksView mark scheme hint▾
Define complementary events and explain their relationship in terms of probability.
Practice Quiz
What is the probability of drawing an Ace from a standard deck of cards?
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