Data Handling and Probability
This domain covers organising data, computing representative values, reading graphs, and calculating probabilities of simple events.
Core skills
- Find the mean, median, and mode, and understand which is affected by extreme values (the mean is; the median is not).
- Read and construct histograms, bar charts, and frequency tables, and interpret relative frequency.
- Compute probability as favourable outcomes over total equally likely outcomes, and use the complement rule P(not A)=1−P(A).
- For two independent events, multiply probabilities.
Common traps
Students often forget to order data before finding the median; with an even count, average the two middle values. When a histogram uses class intervals, the height may represent frequency density rather than frequency, so check the axis label. For probability, ensure outcomes are equally likely; drawing without replacement changes the denominator for the second draw.
Worked example
A bag holds 3 red and 5 blue balls. Two are drawn without replacement. The probability both are red is (3/8)×(2/7)=6/56=3/28, because after one red is removed, 2 red remain among 7 balls.
Rule of thumb: order the data for the median; for successive draws, reduce both the count of favourable items and the total.