{"id":"histogram","model_id":"Histogram","name":"Histogram","summary":"A histogram is a graphical technique that summarizes the distribution of a univariate data set. The range of the data is split into equal-sized bins (classes) and the number of data points falling into each bin is counted, with frequency on the vertical axis and the response variable on the horizontal axis. It shows the center, spread, skewness, outliers and multiple modes of the data.","study_notes":["Purpose stated as (Chambers): graphically summarize the distribution of a univariate data set.","The histogram shows the center (location), spread (scale), skewness, presence of outliers and presence of multiple modes, giving indications of a suitable distributional model.","A probability plot or a goodness-of-fit test can be used to verify the distributional model.","The cumulative histogram is a variant in which the vertical axis gives the count for a bin plus all bins for smaller values of the response variable.","Relative histogram and relative cumulative histogram are variants in which counts are replaced by normalized counts.","Normalization method 1: count in a class divided by the total number of observations, so relative counts sum to one (or 100 if a percentage scale is used).","Normalization method 2: count in the class divided by the number of observations times the class width, so the area under the histogram equals one.","With the area normalization, relative frequencies greater than 1 are permissible; use it when overlaying a probability density or cumulative distribution function.","Histograms can answer: what kind of population distribution the data come from, where data are located, how spread out they are, whether they are symmetric or skewed, and whether outliers exist.","Related techniques listed: box plot and probability plot; frequency plot, stem and leaf plot and density trace are similar in purpose but not discussed in the Handbook.","Demonstrated in the heat flow meter data case study; the sample plot is a histogram of the Michelson speed of light data set.","Available in most general purpose statistical software programs and in most charting, spreadsheet and business graphics programs."],"safety_notes":[],"sources":[{"url":"https://www.itl.nist.gov/div898/handbook/eda/section3/histogra.htm","title":"1.3.3.14. Histogram","accessed":"2026-10-25"}],"verification":{"status":"source_checked","checked_at":"2026-10-25","values":1,"method":"llm_source_check"},"updated_at":"2026-10-25","type":"operational","spec":{"kind":"methodology","related":[]},"url":"https://machineschema.com/operational/histogram","license":"https://creativecommons.org/licenses/by/4.0/"}