PSYC 210 - Variability

# PSYC 210 - Variability - Variability Definition: Spread or...

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Variability Definition: Spread or dispersion of scores, differences among scores Central tendency alone does not provide a complete description of a data set. Central tendency glosses over differences; use one score to represent all Variability points out those differences; describes how different scores are from one another. Measures of central tendency and variability go hand in hand; they complement one another to provide a more complete description of the group of scores. Measures of Variability 1) Range: Distance between the highest and lowest scores = highest score – lowest score Example: 58, 73, 74, 76, 78, 81, 90, 96 Range = 96 – 58 = 38 2) Interquartile range (IQR): the range of the middlemost 50% of scores; range after eliminating the highest 25% of scores and the lowest 25% of scores; the distance between the 1 st quartile and the 3 rd quartile 58, 73, 74, 76, 78, 81, 90, 96 Interquartile range = 85.5 – 73.5 = 12 3) Standard deviation: average distance of the scores from the mean The range gives an answer to a relatively simple question about spread, “How far is it from the highest to the lowest score?” We could ask about spread in a different way, “On average, how far are scores from the mean?” We use a different measure of variability, standard deviation, to answer this. a) Conceptual example for standard deviation:

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## This note was uploaded on 02/23/2012 for the course PSYC 210 taught by Professor Chow during the Fall '08 term at UNC.

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PSYC 210 - Variability - Variability Definition: Spread or...

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