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Variability is a numerical description that refers to the spread values within a given distribution. Variability can be described using four common measures: range, the mean deviation score, standard deviation, and variance. Variance is most useful in determining the overall spread of a data set. Range simply takes two data points, the lowest and highest values, and measures the space between them. The interquartile range also interprets the amount of spread within a set of data by using only the middle 50% of scores. Unlike range, variance takes into account every data point within the set and measures each distance from the mean. Variance is calculated using a number of values from data and the associated distribution. Specifically, variance requires raw data scores and the ...

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