# Lec2

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Unformatted text preview: uely degined Robust MODE Categorical, Numerical No Yes MEDIAN Ordinal, Numerical Yes Yes MEAN Numerical Yes No Words that describe distributions v༇  Unimodal : has one major peak v༇  Bimodal: has two major peaks v༇  Symmetric: there is a symmetry with respect to the middle point v༇  Skewed to the right: when the right tail (larger values) is much longer than the left tail (smaller values) v༇  Skewed to the left Need a measure of spread "GE" and "Philips" Lightbulb Lifetimes (in hours) 20 10 10 0 Frequency 20 0 500 600 700 800 GE 900 1000 540 620 700 780 860 940 Philips “GE” exhibits better quality control: not much variation. “Philips” has more fluctuation although average is same as “GE”. MEAN and MEDIAN do not completely summarize a data set. Also need to know amount of gluctuation. SPREAD: Quartiles & IQR v༇  Define first quartile to be the median of the observations below the median. v༇  Define third quartile to be the median of the observations above the median. |1, 3, 3, 6, 8, 9 M=4.5 Q1=3 Q3=8 The interquartile range IQR is Q3 - Q1 Example: customer satisfaction ratings 20 measurements on the 10 point scale: 9, 8, 3, 8, 10, 9, 8, 9, 5, 8, 1, 10, 8, 10, 7, 8, 9, 10, 5, 9 Quartiles? 1 3 5 5 7 8 8 8 8 8 8 9 9 9 9 9 10 10 10 10 Q1 = (7+8)/2 = 7.5 Md = (8+8)/2 = 8 Q3 = (9+9)/2 = 9 IQR = Q3 - Q1 =...
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## This note was uploaded on 01/15/2014 for the course BUAD 310 taught by Professor Lv during the Fall '07 term at USC.

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