Key Concepts

• The mean, median, and mode are measures of center for a data set.
• If a distribution has extreme values or outliers, the median is a better measure of center.
• If a distribution is of categorical data, only the mode can be calculated.

Glossary

mean: a number that measures the central tendency of the data; a common name for mean is “average.” The sample mean is written as [latex]\overline{x}[/latex] and the population mean is written as [latex]\mu[/latex].

median: a number that separates ordered data into halves; half the values are the same number or smaller than the median, and half the values are the same number or larger than the median. The median may or may not be part of the data.

midpoint: the mean of an interval in a frequency table

mode: the value that appears most frequently in a set of data

statistic: a value calculated from a sample. The sample mean is written as [latex]\overline{x}[/latex].