frequency

1. The number of times that a particular data value is obtained in a sample. For example, the frequency of 5 in the sample 4, 6, 5, 7, 4, 5, 2, 5 is 3. The sum of the frequencies is the sample size. The term is also used in connection with a set of values. For example, the number of people aged between 20 and 30, or the number of people with blue or green eyes. The term relative frequency is used for the ratio (frequency) ÷ (sample size). In the context of a goodness-of-fit test, a frequency is referred to as an observed frequency and usually denoted by O, or f_O. 2. In the context of a time series, the number of cycles per unit time.