Central Tendency and Variability 2-15

# Central Tendency and Variability 2-15 - Measures of Central...

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Measures of Central Tendency and Variability

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Purpose Provide succinct information about: The average, middle, or most frequent score How much the scores differ from one another or from their central tendency
Central Tendency Mean: Average Score N X X = e.g., for self statements: 7 5 35 = = = N X X

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Central Tendency Median: Middle Score The point that cuts a distribution in half half the scores are greater than it half are less than it e.g., for the self statements, M dn = 8
Determining the Median : When Scores in the Middle Are Not Duplicated When there is an odd number of scores: Put the scores in order Pick the middle score When there is an even number of scores: Take the average of the two middle scores E.g., for the scores 3, 9, 4, 11, 8, 7 Mdn = 7.5

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Determining the Median : When Scores in the Middle Are Duplicated Should interpolate: E.g., for difficulty ratings: ( 29 ( 29 i n n N L Mdn w L - + = 5 .
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## This note was uploaded on 04/16/2008 for the course PSYC 100 taught by Professor ? during the Spring '08 term at San Diego.

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Central Tendency and Variability 2-15 - Measures of Central...

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