Statistics · Grades 11 to 12
Probability
Simple events and independent events.
The idea
Probability measures how likely an event is. It is the number of favourable outcomes divided by the number of possible outcomes.
For independent events, multiply the probabilities. Two events are independent when one does not change the chance of the other.
Worked examples
- How to Find the Probability of a Simple Event Find the probability of rolling an even number on one die. Three steps, the favourable-over-total rule, and the counting mistakes to avoid.
- Find the Probability of Two Independent Events Find the probability of heads then a 6. Three steps, the multiplication rule, and the add-instead-of-multiply mistake to avoid.
- How to Find the Probability of a Dice Sum Find the probability that two dice sum to 7. Three steps that count the 36 pairs, and the double-counting mistakes students make.
Practice this topic
6 problems with answers.