POLS 3650 Lecture 8: Univariate Statistics III: Measures of Dispersion
3 Feb 2017
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Lecture 8: univariate statistics iii: measures of dispersion. A measure of dispersion gives information on the heterogeneity of the cases under investigation. The larger the measure of dispersion, the more the cases differ from each other. Knowledge of coding is necessary for an exact interpretation of a measure of dispersion: measures of dispersion tend to be larger for variables with a large number. As with all statistics, the level of measurement is crucial in determining which measures of possible value of dispersion can meaningfully be calculated. Ordinal: range, quintile range (and variation ratio) Interval/ratio: standard deviation (and quintile range, variation ratio) Variation ratio = the proportion of valid cases that does not have the modal value. Range= the difference between the highest and lowest value. As the number of possible values decreases, and the total number of cases increases, this statistic becomes less and less useful.
