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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
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.
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
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)
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.”
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 = 
2
( X i   )2


N
2
(
X

X
)

i
Sample variance = s 2 
n 1

SSX
df
SSX   ( X i  X ) 2
SSX: Sum of Squared deviations for X
df  deg rees of freedom
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.
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.