Relative frequency is a term used in probability theory and statistics to describe the ratio of the number of outcomes in which a specified event occurs to the total number of trials or outcomes in an experiment. It is also known as empirical probability or experimental probability. Relative frequency is an experimental probability, not a theoretical one, and can vary each time an experiment is repeated.

To calculate the relative frequency, we need to know the frequency count for the total population and the frequency count for a subgroup of the population. The formula for calculating the relative frequency of a subgroup is:

Relative Frequency = Subgroup Count / Total Count

Relative frequency is usually expressed as a decimal or percentage, and all the relative frequencies add up to 1 (except for any rounding error) . It is a useful way to measure how often a particular event occurs against total occurrences.

Relative frequency is used to estimate probabilities from experience and observation, and it can give us an idea of the trends or center of a data set. It is a very useful way to talk about data in a meaningful way that anyone can understand.