Variability Class Notes

# Variability Class Notes - Variability Definition and...

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Variability Definition and Context: - Quantitative measure of the spread (or clustering) of our data - In relation to central tendency --- can tell us how much variation there is around a measure of CT - Range, IQR, std deviation/variance 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 More to note about the Range 1. Crude and unreliable Distribution 1 : 1, 20, 40, 60, 100 Range= 100 – 1= 99 Distribution 2 : 1, 2, 2, 4, 100 Range= 100 – 1= 99 Distribution 3 : 1, 98, 99, 100, 100 Range= 100 – 1= 99 2) Interquartile range (IQR): First quartile Q1 the score that separates the lowest 25% of the distribution from the rest Second quartile Q2 score that separates the distribution into two half or 50% (median) Third quartile Q3 score that separates the bottom 75% of the distribution from the top quarter **IQR is the distance between the 1 st and 3 rd quartile: IQR = Q3 – Q1 Example: 58, 73, 74, 76, 78, 81, 90, 96 Q2 = median = 77 Q1 = 73.5, Q3 = 85.5 IQR = 85.5-73.5 = 12 More to note about IQR:

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Variability Class Notes - Variability Definition and...

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