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Lecture 3 - variability Percentile ranks and standard score

# Lecture 3 - variability Percentile ranks and standard score...

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Unformatted text preview: Variability, Group Variability, Group position, Standard score position, Standard score Spring 2008 Spring 2008 KIN 369 KIN 369 Variability Variability ● A second type of descriptive statistic. ● Describes spread or heterogeneity of scores. Measures of Variability Measures of Variability ● Range ● Standard Deviation ● Variance Range Range ● Range = high score - low score. ● Unstable because it depends on only two scores. Range = High score - Low Range = High score - Low score score 1 2 3 100 75 51 50 50 50 50 50 50 25 49 Range: 100 50 2 Standard Deviation (s) Standard Deviation (s) ● Average deviation of each score from the mean. ● Minimum value of s = 0. ● Larger s, more heterogeneous the group. = standard deviation of population s = standard deviation of sample σ Standard Deviation (s) Standard Deviation (s) ● Definitional Formula: s = √ Σ (X - X) 2 ÷ (n - 1) Calculate the Standard Deviation Calculate the Standard Deviation s = √ Σ (X - X) 2 ÷ (N - 1) X (X - X) (X - X) 2 5 4-1 1 2-3 9 9 4 16...
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Lecture 3 - variability Percentile ranks and standard score...

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