Experimental Probability
Maths: Edexcel IGCSE Higher, topic 6.3.3
Relative and Expected Frequency
The relative frequency of each outcome can be calculated after a probability experiment.
Formula
- Relative frequency = frequency ÷ number of trials.
- If a dice was rolled 150 times and the result was a 4 in 25 of those rolls then the relative frequency of 4 was 25 ÷ 150 = 1⁄6.
Expected frequency
- The relative frequency of an outcome in one experiment can be used to calculate the expected outcomes of future experiments:
- expected frequency = relative frequency × number of trials
Fair or biased?
- If the relative frequency of a result is very different from what you’d expect from a fair dice or coin then you can conclude that the dice or coin is probably biased.
- Otherwise you can conclude that it is probably fair.
Test yourself on Experimental Probability
What is the relative frequency of picking a red ball from a bag if a red ball is pulled out of a bag 100 times in 400 trials?