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074 - 09:00:00 ← Lower Quartiles = QL • The median of...

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Statistics 13/09/2007 09:00:00 Measures of Variability Range = Largest value – Smallest value o Advantage: Easy to compute o Disadvantage: Only use two values WB7-1 o Sample A: Range = 510 – 485 = 25 o Sample B: Range = 1000 – 0 = 1000 Variance = “Average” squared deviation from the mean (7.2) sample variance = s squared Example WB7-1 Variance of Sample A: 112.5 Variance of Sample B: 205,000 (computations not shown) The numbers in both samples represent credit card balances in dollars Variances are measured in square units Sample Variance Formula #1 X Deviation (x-x) Squared Deviation 0 0 – 10 = -10 (-10)squared = 100 10 10 – 10 = 0 (0)squared = 0 20 20 – 10 = 10  (10) squared = 100 30 0 200 Sample Variance Formula #2 X Xsquared 0 0 squared = 0 10 10 squared = 100 20 20 squared = 400  30 500
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Quartiles
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Unformatted text preview: 13/09/2007 09:00:00 ← Lower Quartiles = QL • The median of Minimum and the Median ← ← Upper Quartile = QU • The median of Median and the Maximum ← ← Computing QL and QU • Rank data in order from smallest (1) to largest (n) • Find overall median • QL = median of values ranked below the overall median • QU = median of values ranked above the overall median ← ← Five-Number Summary: n even • Ordered data: 1 2 3 4 5 6 • Overall Median: (3+4)/2 = 3.5 • QL = 2 / QU = 5 • Five number summary: 1 , 2 , 3.5 , 5 , 6 ← ← Five-Number Summary: n odd • Ordered data: 1 2 3 4 5 6 7 • Overall Median: 4 • QL = 2 / QU = 6 • Five number summary: 1 , 2 , 4 , 6 , 7 13/09/2007 09:00:00 ←...
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