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Unformatted text preview: 2006 by Harvey A. Singer 1 OM 210 Statistical Analysis for Management Data Summarization: Part 2: Measures of Dispersion and Variability Dr. Harvey A. Singer School of Management George Mason University 2006 by Harvey A. Singer 2 Purpose With measures of central tendency, we looked at how the similar the data are to each other. In terms of how well the data group or cluster about central values. For different notions of center. Mean vs. median vs. mode vs. etc. Now, with measures of variability, we will look at how different the data are from each other. In terms of how poorly the data cluster about the center. Measure how widely scattered or dispersed are the data about the central values. 2006 by Harvey A. Singer 3 Numerical Data Properties and Measures Coeff. of Variation Numerical Data Mean Median Mode Midrange (Quartiles) Midquartile Central Tendency Range Interquartile Range Variance Standard Deviation Variability Skew Shape Grouped Data (Quartiles) Symmetric Weighted mean Clustering 2006 by Harvey A. Singer 4 Project Durations Sample of n = 11 projects for their completion times in whole days. Data in raw form (as collected). 24, 26, 24, 20, 27, 27, 28, 31, 49, 33, 38 Data rankordered and listed in an ordered array. 20, 24, 24, 26, 27, 27, 28, 31, 33, 38, 49 x min x max 2006 by Harvey A. Singer 5 Sampled Project Durations How variable is project duration? Measure how different are the sampled data values. How is data variability measured? What are the different variability measures? How calculated? What do they measure? How are they used? How representative is the calculated mean project duration of the sampled projects? And of all projects? In other words, how reliable is the mean project duration? 2006 by Harvey A. Singer 6 Sampled Apartment Rents Given below is a sample of monthly rent values ($) for onebedroom apartments. The data is a sample of 70 apartments in a particular city. The data are presented in the table below in numericallyascending rank order (left to right, top to bottom). 425 430 430 435 435 435 435 435 440 440 440 440 440 445 445 445 445 449 450 450 450 450 450 450 450 460 460 460 465 465 465 470 470 472 475 475 475 480 480 480 480 485 490 490 490 500 500 500 500 510 510 515 520 525 525 535 549 550 570 570 575 575 580 590 600 600 600 600 615 615 2006 by Harvey A. Singer 7 Sampled Apartment Rents How variable is apartment rent? Measure how different are the rent data values. How is data variability measured? What are the different variability measures? How calculated? What do they measure?...
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This note was uploaded on 01/26/2011 for the course OM 210 taught by Professor Singer during the Fall '08 term at George Mason.
 Fall '08
 SINGER

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