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lec5 - STATISTICS 13 STATISTICS Lecture 5 Oct 4 2010 Shape...

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STATISTICS 13 STATISTICS 13 STATISTICS 13 Lecture 5 Lecture 5 Oct. 4, 2010 Oct. 4, 2010
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Review Shape of the data -Bell shaped -Skewed -Bimodal Measures of center Arithmetic Mean – Median – Mode Effects of outliers
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Effect of Skewness Symmetric : mean median Skewed right : mean > median Skewed left : mean < median Mean = Median Median Median Mean Mean
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Examples Example1: “Age of CEO”: nearly symmetric Example2: “ Box Office”: skewed to right Age Percent 76 67 58 49 40 31 76 67 58 49 40 31 40 30 20 10 0 40 30 20 10 0 Histogram of Age Mean=51.5 Median=50 Revenue Frequency 20000 15000 10000 5000 0 9 8 7 6 5 4 3 2 1 0 Histogram of Revenue Mean=4237.8 Median=2253.5
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Average household income Which average? Do not get manipulated…
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Average household income
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Measures of Variability A quantitative measure that describes the spread or dispersion of the data along the horizontal axis of the data distribution Data sets may have the same center (e.g., mean), but look different because the way the numbers spread out from the center
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Measures of Variability (Cont.) Example: two data sets -data set one: 1,2,3,3,4,4,4,4,5,5,5,5,5,5,6,6,6,6,7,7,8,9 -data set two: 3,4,4,5,5,5,6,6,7 -both have mean =5; but data set one has a larger spread than data set two
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