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Grade 8 · Data · Multiple-Event Probability

Map Compound Probability

Tree diagrams show how choices branch through a sequence. Probabilities along a branch multiply, while probabilities of separate successful branches add.

The big idea

The sample space controls the calculation

For independent events, earlier outcomes do not change later probabilities. Without replacement, the remaining sample changes and events become dependent.

Work it through

Find the probability of heads then an even die roll

  1. 1. P(heads) = 1/2.
  2. 2. P(even on a fair die) = 3/6 = 1/2.
  3. 3. The events are independent, so multiply: 1/2 × 1/2 = 1/4.
  4. 4. A sample-space diagram confirms 3 successful outcomes among 12 equally likely pairs.