# 3.2 - Measures of Variation.pdf - Measures of Variation...

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Measures of VariationSection 3.2Objectives:Range, Variance, Standard Deviation.Empirical Rule.Def:Ameasure of variationis a value describing the dispersion or deviation of the data.Note: We'll look at range, standard deviation and variance.Def:Therangeof a set of data values is the difference between the maximum data value and theminimum data value.Range = (maximum data value) - (minimum data value)Do you think the range is resistant to extreme values?Ex: 1) Find the range of the following samples:a) {1,2,3,4,5}b) {1,2,3,4,5,75}Note: Like the median, range doesn't use all of the data values (it only uses two), so isn't often used todescribe the variation of a data set. The standard deviation is a measure of variation that uses all valuesin the data set.Def:Thestandard deviationof a set of sample values is a measure of how much data values deviateaway from the mean.The greek letter,σ(sigma), represents the population standard deviation.

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