What is Relative Frequency?
The relative frequency of an outcome is the frequency of that outcome divided by the total number of trials. It can be expressed as a fraction, decimal, or percentage.
Whenever you run an experiment — flipping a coin, rolling a die, surveying people — you record how often each outcome occurs. Relative frequency turns that raw count into a proportion, making it easy to compare results even when experiments have different numbers of trials.
The formula is straightforward:
Because every outcome's relative frequency is a fraction of the whole, all the relative frequencies in an experiment must add up to 1 (or 100%).
Relative frequency is sometimes called experimental probability because it gives us a probability value based on actual results, not theory.
Key Vocabulary: Trials, Outcomes, and Frequency
Before calculating relative frequencies, you need to be comfortable with three core terms:
A single repetition of an experiment. The total number of trials is how many times the experiment is carried out altogether.
One possible result for a single trial. For example, when tossing a coin the outcomes are heads and tails.
The number of times a particular outcome is observed across all trials.
Think of it this way: if you roll a die 300 times, each individual roll is one trial, the numbers 1–6 are the possible outcomes, and the frequency of, say, rolling a 4 is how many of those 300 rolls actually showed a 4.
Imagine tallying votes in a class election. Each ballot cast is a trial, each candidate is an outcome, and the vote count for each candidate is the frequency. The relative frequency would be each candidate's share of the total vote — their percentage of support.
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