AQA GCSE Mathematics · 8300
Specification P9 · Paper 1, Paper 2, Paper 3
The number of occurrences predicted for an event over a stated number of trials, found from probability multiplied by the number of trials.
Revise: Conditional ProbabilityProbabilities and percentages can be converted into expected frequencies by choosing a convenient total. For example, if a condition affects 1% of a population, a model based on 10,000 people gives an expected 100 people with the condition and 9,900 without it. If 90% of those with the condition test positive, the expected number of true positives is 90.