Frequency (statistics)

Frequency (statistics)

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

We speak of absolute frequencies, when the counts ni themselves are given and of (relative) frequencies, when those are normalized by the total number of events:

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

Taking the fi for all i and tabulating or plotting them leads to a frequency distribution.

The relative frequency density of the occurrence of an event is the score divided by the total number of observations.

For example: If the lower extreme of the class you are measuring the density of is 15 and the upper extreme of the class you are measuring is 30, given a relative frequency of 0.0625, you would calculate the frequency density for this class to be:

Relative frequency / (Upper extreme of class − lower extreme of class) = density
0.0625 / (30 − 15) = 0.0625 / 15 = 0.0041666.. That is: 0.00417 to 5 decimal places.

In biology, relative frequency is the occurrence of a single gene in a specific species that makes up a gene pool.

The limiting relative frequency of an event over a long series of trials is the conceptual foundation of the frequency interpretation of probability. In this framework, it is assumed that as the length of the series increases without bound, the fraction of the experiments in which we observe the event will stabilize. This interpretation is often contrasted with Bayesian probability.

See also


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • frequency distribution — Statistics. the correspondence of a set of frequencies with the set of categories, intervals, or values into which a population is classified. [1890 95] * * * In statistics, a graph or data set organized to show the frequency of occurrence of… …   Universalium

  • frequency — [frē′kwənsfrē′kwən sē] n. pl. frequencies [ME < Fr < L frequentia < frequens: see FREQUENT] 1. Obs. a) the condition of being crowded b) a crowd 2. the fact of occurring often or repeatedly; frequent occurrence 3 …   English World dictionary

  • frequency curve — Statistics. a curve representing the frequency with which a variable assumes its values. [1890 95] * * * …   Universalium

  • frequency polygon — Statistics. a frequency curve consisting of connected line segments formed by joining the midpoints of the upper edges of the rectangles in a histogram whose class intervals are of uniform length. [1895 1900] * * * …   Universalium

  • frequency function — Statistics. See probability density function (def. 2). * * * …   Universalium

  • frequency function — Statistics. See probability density function (def. 2) …   Useful english dictionary

  • statistics — /steuh tis tiks/, n. 1. (used with a sing. v.) the science that deals with the collection, classification, analysis, and interpretation of numerical facts or data, and that, by use of mathematical theories of probability, imposes order and… …   Universalium

  • Frequency distribution — In statistics, a frequency distribution is an arrangement of the values that one or more variables take in a sample. Each entry in the table contains the frequency or count of the occurrences of values within a particular group or interval, and… …   Wikipedia

  • Frequency probability — Statistical probability redirects here. For the episode of Star Trek: Deep Space Nine, see Statistical Probabilities. John Venn Frequency probability is the interpretation of probability that defines an event s probability as the limit of its… …   Wikipedia

  • Frequency analysis — In cryptanalysis, frequency analysis is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers.this is wrong is based on the fact that, in any given stretch of… …   Wikipedia