Interquartile Range

Descriptive statistics summarize or describe data sets using measures of central tendency and dispersion. Measures of central tendency (e.g., mean, median) identify the dominant, representative, or typical data value, whereas measures of dispersion (e.g., standard deviation) communicate the spread or variability in the data set. Interquartile range (IQR) is a measure of dispersion that encompasses the middle half of the data by taking the difference between the data values positioned at the 25th and 75th percentiles. The IQR accentuates the central range of the data rather than the maximum and minimum values. This entry explains how to calculate the IQR as well as how IQRs are commonly displayed graphically.

To determine the IQR, the data are first arranged in ascending order and subdivided into four ...

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