Objectives To calculate measures of central tendency
To draw and interpret box-and-whisker plots
People often refer to the mean as the average. The mean is only one of the measures considered the average, a measure of the center of a set of data.
Essential Understanding You can describe and compare sets of data using various statistical measures, depending on what characteristics you want to study.
Statistics is the study, analysis, and interpretation of data. One way to analyze data is by finding a measure of central tendency. A measure of central tendency indicates the “middle” of the data set. The mean, median, and mode are the most common measures of central tendency.
Measure | Definition | Example, using 1, 2, 3, 3, 4, 5, 5, 9 |
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Mean |
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Median | for a data set listed in order: the middle value for an odd number of data values; the mean of the two middle values for an even number of data values | For 1, 2, 3, 3, 4, 5, 5, 9, the middle two values are 3 and 4. The median is their mean
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Mode | the most frequently occurring value(s) | Two modes: In 1, 2, 3, 3, 4, 5, 5, 9, both 3 and 5 occur twice. |