Probability Formulae

This lesson introduces the key probability formulae required for Edexcel A-Level Statistics, linking them to real-life applications such as weather forecasting, medical testing, quality control, insurance, and sports analytics. Students begin with a starter activity that revisits prior knowledge of probability and explores how probabilities are used to support decision-making in everyday situations. The lesson develops understanding of probability notation and the main formulae, including the complement rule, addition laws for mutually exclusive and non-mutually exclusive events, multiplication laws for independent events, and conditional probability. Visual representations such as Venn diagrams and probability trees are used to help students organise information, identify relationships between events, and select appropriate methods. Students then apply these formulae through progressively challenging practice questions and Edexcel-style examination problems, supported by fully worked solutions that model clear reasoning and effective exam technique. By the end of the lesson, students will be able to confidently choose and apply the correct probability formula in a range of statistical contexts and examination scenarios.