Frequency (statistics)

In statistics the frequency (or absolute frequency) of an event $i$ is the number $n_i$ of times the event occurred in an experiment or study. These frequencies are often graphically represented in histograms.

The relative frequency (or empirical probability) of an event refers to the absolute frequency normalized by the total number of events:

$f_i = \frac{n_i}{N} = \frac{n_i}{\sum_i n_i}.$

The values of $f_i$ for all events $i$ can be plotted to produce a frequency distribution.

Under the frequency interpretation of probability, it is assumed that as the length of a series of trials increases without bound, the fraction of experiments in which a given event occurs will approach a fixed value, known as the limiting relative frequency. This interpretation is often contrasted with Bayesian probability.

See also

• Probability density function
• Frequency
• Law of large numbers
• Statistical regularity
• Cumulative frequency analysis