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Chapter 2: Descriptive Statistics Adding MegaStat in Microsoft Excel 2010 http://blog.wentoday.com/?p=640 2.1 Measures of Central Tendency Mode: The most frequently occurring number Learning Activity 2.1-1 Calculate the mode Open Price.xls!Data_sorted Use the Excel MODE() function Mode_Solution Learning Activity 2.1-2 Open Bedrooms.xls!Data_sorted Use the Excel MODE() function Mode_Solution
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Median and Quartiles Median: the middle number of a set of data Learning Activity 2.1-3 Calculate the median Open Price.xls!Data_sorted. Find the median by taking the mean of the middle two numbers. Use the Excel MEDIAN() function. Use MegaStat|Descriptive Statistics. Median_Solution Learning Activity 2.1-5 Calculate the quartiles Open Quartiles.xls!Data. Use MegaStat|Descriptive Statistics Use Excel’s QUARTILE() function. Sort the Price variable (ascending) and verify the 1st quartile is between 31st and 32nd values (1/4 of the values are below) and the 3rd quartile is between 93rd and 94th values.
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Mean Graphical Representation of the Mean Data representation of Mean1.xls 4, 4, 6, 2, 5, 9, 5, 7, 5, 2, 14, 7, 14, 7, 7, 2, 9, 8 The mean as the center of mass
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Outliers Q1 = 25th percentile (the value below which 25% of the data fall) Q3 = 75th percentile H = Q3 – Q1 (the interquartile range, a measure of dispersion) An outlier is defined as any value less than Q1 – 1.5*H Or greater than Q3 + 1.5*H. An extreme outlier is defined as any value less than Q1 – 3.0*H or greater than Q3 – 3.0*H. ( http://www.itl.nist.gov/div898/handbook/prc/section1/prc16.htm ) http://www.itl.nist.gov/div898/handbook/prc/section1/prc16.htm Note: To use this rule, you assumed your data are normally distributed. Learning Activity 2.1-7 Outliers, mean and median Open Dataset1.xls!Data Use MegaStat|Descriptive Statistics specify A3:B27 as the input range select Definitional form and “Median and Quartiles.”
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2.2 Measure of Variatiion Range, Mean Deviation, and Mean Absolute Deviation Learning Activity 2.2-1, -2, & -3 Open Mean1.xls!Data. Calculate Min(), Max() and range Calculate Mean deviation Calculate Mean absolute deviation (MAD) (use =ABS()). Variance and Standard Deviation Population variance = Sample variance = SSX: Sum of Squared deviations for X
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Learning Activity 2.2-5 Calculate variation by using Excel and Megastat Open Open Stdev2.xls!Data.. In cells F21:F23 use DEVSQ(), VAR(), and STDEV() to calculate SSX, variance and s.d., respectively. Learning Activity 2.2-6 Open Stdev3.xls!Data. Copy/Paste F2:F19 into B2:B19 Do the same for other data Learning Activity 2.2-7 Graphical interpretation of S. D. Open GraphicSD.xls!Data.
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Sample MegaStat Output Learning Activity 2.3-1 Descriptive Statistics Open Variation.xls!Data. Use MegaStat|Dexcriptive Statistics, specify B3:C13 as the input range and select Median...and SSX. Scatterplot Learning Activity 2.4-3 Open RealEstateData.xls!Data. Use MegaStat | Correlation/Regression | Scatterplot. Use SqrFt as the horizontal axis and Price the vertical. Uncheck the “Plot linear regression line” box. Put a title in the title box. Redo the previous step, checking the “Plot linear regression line” box.
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