If you know the probability of an event, you can predict how often it should happen. Expected frequency = probability × number of trials.
A spinner lands on red with probability 0.25. Spun 64 times, you expect about 0.25 × 64 = 16 reds. Real results vary, so the expected frequency is the best estimate, not a promise. Relative frequency, the number of times it happened ÷ the number of trials, gets closer to the probability as you do more trials.
Worked example
A fair die is rolled 60 times. How many sixes would you expect?
- P(six) = 1/6.
- 1/6 × 60 = 10.
Answer:10 sixes
Key words
- trial
- one go of an experiment
- expected frequency
- how many times you expect an event
- relative frequency
- the fraction of trials when it happened
Practise this
New questions every time.
Common Core-referenced: 7.SP.C.6