Expected Frequency — How Often Over Many Tries (Grade 7)
If you repeat an experiment many times, the expected number of times an event happens is its probability times the number of trials. Roll a die 60 times: since P(rolling a 4) = 1/6, you'd expect about 1/6 × 60 = 10 fours. It's an estimate of the long-run count, not a guarantee for any single run.
Understanding expected frequency
If you repeat an experiment many times, the expected number of times an event happens is its probability times the number of trials. Roll a die 60 times: since P(rolling a 4) = 1/6, you'd expect about 1/6 × 60 = 10 fours. It's an estimate of the long-run count, not a guarantee for any single run.
Key Idea
If you repeat an experiment many times, the expected number of times an event happens is its probability times the number of trials. Roll a die 60 times: since P(rolling a 4) = 1/6, you'd expect about 1/6 × 60 = 10 fours. It's an estimate of the long-run count, not a guarantee for any single run.
Seeing it in action
Worked example
Roll a fair die 60 times — expected number of 4s?
P(4) = 1/6. Expected = 1/6 × 60 = 10.
Expected count = probability × number of trials.
Try a few
Flip a coin 50 times — expected heads?
1/2 × 50.
Spinner P(gold)=1/4, spun 20 times — expected golds?
P(red)=1/3, 30 draws — expected reds?
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