Probability Basics
Year 8 📈 Statistics & Probability Probability scale, single events, complementary events.
🎲 Probability Scale
Probability measures how likely an event is, on a scale from 0 (impossible) to 1 (certain).
Probability Formula
$$P(\text{event}) = \frac{\text{Number of favourable outcomes}}{\text{Total number of outcomes}}$$🎯 Complementary Events
Complement Rule
$$P(A') = 1 - P(A)$$Example: P(rain) = 0.3 → P(no rain) = 1 − 0.3 = 0.7
🌳 Combined Events
And / Or Rules
$$P(A \text{ and } B) = P(A) \times P(B) \quad \text{(independent events)}$$
$$P(A \text{ or } B) = P(A) + P(B) - P(A \text{ and } B)$$
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
Interactive Demonstration — Probability Basics
Adjust the slider to set P(A), then click Spin!
🎲 Probability Spinner