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# lect5 - Contingency Tables Strength of Association Simpsons...

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Contingency Tables Strength of Association Outline Contingency Tables Mosaic Plots Strength of Association Chi-Squared Statistics Cramer’s V Simpson’s Paradox 1 / 15 ISOM 2500 Lect 5: Association btw Categorical Variables

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Contingency Tables Strength of Association Mosaic Plots Which hosts send more buyers to Amazon.com? To answer this question we must gather data on two categorical variables: Host and Purchase Host identiﬁes the originating site: MSN, RecipeSource, or Yahoo; Purchase indicates whether or not the visit results in a sale Consider two categorical variables simultaneously Contingency table: a table that shows counts of cases on one categorical variable contingent on the value of another (for every combination of both variables) Cells in a contingency table are mutually exclusive , i.e, each case appears in only one cell of the table. 2 / 15 ISOM 2500 Lect 5: Association btw Categorical Variables
Contingency Tables Strength of Association Mosaic Plots Contingency Table for Web Shopping The following contingency table summarizes n = 17,619 visits to amazon.com during the fall season. 1 Marginal and Conditional Distributions Marginal distributions appear in the “margins” of a contingency table and represent the totals (frequencies) for each categorical variable separately Conditional distributions refer to counts within a row or column of a contingency table, i.e., restricted to cases satisfying a condition. 1 Use Analyze > Fit Y by X to get this display. To get the contingency table with only counts, uncheck the percentage items by clicking on the red button beside the title “Contingency Table”. 3 / 15 ISOM 2500 Lect 5: Association btw Categorical Variables

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Contingency Tables Strength of Association Mosaic Plots Percentages in Tables By adding the right percentages to the table, we can see that Host and Purchase are associated. We have to decide which percentages to add. By default, JMP shows all of the percentages.
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• Spring '11
• a
• Pearson's chi-square test, btw Categorical Variables, Association btw Categorical, Association Simpson, Contingency Tables Strength

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lect5 - Contingency Tables Strength of Association Simpsons...

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