QMS 102 Lecture 5: Lecture 5 Notes
29 Oct 2016
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Measures of variability: range, interquartile range (iqr, variance, standard deviation, coefficient of variation. Variation range variance standard deviation coefficient of variation. Measures of variation give information on the spread or variability or dispersion of the data: could have same centre, different variation. Measures of central location fail to tell the whole story about the distribution (wider is larger standard deviation, taller is smaller standard deviation. Why not use mean: observe two data sets: Small variability: the average value provides a good representation of the observations in the data set. Large variability: the same average value does not provide as good representation of the observations in the data set as before. Difference between the largest and the smallest values. Range = xlargest xsmallest, largest value (13) smallest value (1) = 12 (range) Measures of variation: why the range can be misleading. Ignores the way in which data are distributed. The range is the simplest measure of variability, and calculated as:
