Ch5_Variability

Ch5_Variability - Chapter 5 Measures of Variability...

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Chapter 5 Measures of Variability
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Variability and Range Variability : How much scores vary from each other. Range : The spread, or dispersion, from the highest to the lowest score. Range = X highest - X lowest
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Quartile Ranges Interquartile range : used with ordinal data X 75 - X 25 which provides the range of scores of 50% of the subjects around the median. Semi-Interquartile range : (X 75 - X 25 ) / 2 provides the range of the scores of 50% of the subjects above and below the median
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Variance Variance is the most used statistic to measure the variability of a variable. Variance can be obtained by subtracting the mean of a distribution from each score in the distribution, squaring each difference, summing the differences, and then dividing the sum by the number of scores in the distribution.
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Sample Variance and Population variance Population 2 2 2 D Sample 2 2 N ) X ( Variance Population N X N ) X X ( S Variance Sample - = = = - = = μ σ
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Ch5_Variability - Chapter 5 Measures of Variability...

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