Probability

Probability is a self-contained unit that rewards clear, organised working. It covers the probability scale, sample spaces, relative frequency, mutually exclusive and independent events, tree diagrams, Venn diagrams with set notation, conditional probability and two-way tables.

Basic probability, the probability scale and two-way tables are reliable Foundation marks. Tree diagrams are the crossover topic that appears on almost every paper, and the most common mistake is multiplying along branches without checking whether events are independent or without replacement. Venn diagrams, set notation and conditional probability are the Higher-tier focus and are increasingly popular with examiners. Probability uses fractions, decimals and percentages constantly, so fluency with the number unit pays off directly here.