Chapter 2b: descriptive stats, tabular & graphical displays môn Xác suất thống kê| Trường Đại học Ngoại Thương

entials of deSrlide n s by John Business Statistics (6e) Loucks
on, Sweeney, Williams, Camm, Cochran St. Edward’s 7 Cengage Learning University by John Loucks wards University
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Statistics for Business and Economic apter 2, Part B
scriptive Statistics: Tabular and Graphical Displays
mmarizing Data for Two Variables Using Tables
mmarizing Data for Two Variables Using Graphical Displays
a Visualization: Best Practices in Creating Effective Graphical Displa
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Statistics for Business and Economic
mmarizing Data for Two Variables sing Tables
us far we have focused on methods that are used to summarize the data for ne variable at a time.
en a manager is interested in tabular and graphical methods that will help
nderstand the relationship between two variables.
sstabulation is a method for summarizing the data for two variables.
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Statistics for Business and Economic osstabulation
rosstabulation is a tabular summary of data for two variables. sstabulation can be used when:
one variable is categorical and the other is quantitative,
both variables are categorical, or
both variables are quantitative.
left and top margin labels define the classes for the two variables.
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Statistics for Business and Economic osstabulation mple: Finger Lakes Homes
The number of Finger Lakes homes sold for each style and price for the
past two years is shown below. Price Home Style
Range Colonial Log Split A-Frame Total < $250,000 18 6 19 12 55 > $250,000 12 14 16 3 45 Total 100 30 20 35 15
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Statistics for Business and Economic osstabulation mple: Finger Lakes Homes
Insights Gained from Preceding Crosstabulation
•The greatest number of homes (19) in the sample are a split-level style
and priced at less than $250,000.
•Only three homes in the sample are an A-Frame style and priced at $250,000 or more.
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Statistics for Business and Economic
osstabulation: Row or Column Percentages
nverting the entries in the table into row percentages or column
ercentages can provide additional insight about the relationship between e two variables.
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Statistics for Business and Economic osstabulation: Row Percentages mple: Finger Lakes Homes Price Home Style
Range Colonial Log Split A-Frame Total < $250,000 32.73 10.91 34.55 21.82 100 > $250,000 26.67 31.11 35.56 6.67 100
Note: row totals are actually 100.01 due to rounding.
(Colonial and > $250K)/(All > $250K) x 100 = (12/45) x 100
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Statistics for Business and Economic
osstabulation: Column Percentages mple: Finger Lakes Homes Price Home Style
Range Colonial Log Split A-Frame < $250,000 60.00 30.00 54.29 80.00 > $250,000 40.00 70.00 45.71 20.00 Total 100 100 100 100
(Colonial and > $250K)/(All Colonial) x 100 = (12/30) x 100
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Statistics for Business and Economic
osstabulation: Simpson’s Paradox
a in two or more crosstabulations are often aggregated to produce a ummary crosstabulation.
must be careful in drawing conclusions about the relationship between the
wo variables in the aggregated crosstabulation.
ome cases the conclusions based upon an aggregated crosstabulation can
e completely reversed if we look at the unaggregated data. The reversal of
onclusions based on aggregate and unaggregated data is called Simpson’s aradox.
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Statistics for Business and Economic
mmarizing Data for Two Variables ing Graphical Displays
most cases, a graphical display is more useful than a table for recognizing atterns and trends.
playing data in creative ways can lead to powerful insights.
tter diagrams and trendlines are useful in exploring the relationship between wo variables.
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Statistics for Business and Economic atter Diagram and Trendline
catter diagram is a graphical presentation of the relationship between two uantitative variables.
e variable is shown on the horizontal axis and the other variable is shown on e vertical axis.
general pattern of the plotted points suggests the overall relationship etween the variables.
endline provides an approximation of the relationship.
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Statistics for Business and Economic atter Diagram ositive Relationship y x
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Statistics for Business and Economic atter Diagram Negative Relationship y x
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Statistics for Business and Economic atter Diagram Apparent Relationship y x
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Statistics for Business and Economic atter Diagram mple: Panthers Football Team
The Panthers football team is interested in investigating the relationship,
if any, between interceptions made and points scored. x= Number of y= Number of Interceptions Points Scored 1 14 3 24 2 18 1 17 3 30
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Statistics for Business and Economic atter Diagram and Trendline y 35 30 25 20 15 10 5 Number of Points Scored 0 x 12 3 4 Number of Interceptions
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Statistics for Business and Economic ample: Panthers Football Team
ghts Gained from the preceding Scatter Diagram
The scatter diagram indicates a positive relationship between the number of
interceptions and the number of points scored.
Higher points scored are associated with a higher number of interceptions.
The relationship is not perfect; all plotted points in the scatter diagram are not on a straight line.
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Statistics for Business and Economic de-by-Side Bar Chart
de-by-side bar chart is a graphical display for depicting multiple bar charts n the same display.
h cluster of bars represents one value of the first variable.
h bar within a cluster represents one value of the second variable.
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Statistics for Business and Economic de-by-Side Bar Chart Finger Lake Homes 20 18 16 < $250,000 14 > $250,000 12 10 Freq 8 uency 6 4 2 Home Styl
Colonial Log Split-Level A-Frame
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