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Part%209%20Research%20Strategies%20and%20Validity0

# 1 2 calculatingthevariance calculatingthevariance

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Unformatted text preview: of Observations” Measures of dispersion • Dispersion/Variability refers to how much the scores in a distribution differ from the mean – – – Variance Standard deviation Range Measures of dispersion: Range Measures of dispersion: Range • Difference between biggest and smallest score – Easy to calculate, but is only based on 2 scores • Not very informative as it ignored most of the data Measures of dispersion: Variance Measures of dispersion: Variance • The sum of the squares of the deviations about the mean, divided by the number of scores minus 1 – Involves calculation if the deviation scores Variance = s 2 ∑(X − M ) = n −1 2 Calculating the variance Calculating the variance 1: Calculate the mean value of X s 2 ∑(X − M ) = n −1 2 Calculating the variance Calculating the variance 2: Calculate the deviation score separately for each value of X s 2 ∑(X − M ) = n −1 2 Calculating the variance Calculating the variance 3: Square the deviation score for each value of X s 2 ∑(X − M ) = n −1 2 Cal...
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