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Analysis of a 2x2 Contingency Table

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Occasional Contributor
Posts: 13

Analysis of a 2x2 Contingency Table

[ Edited ]

I want to create a crosstabulation table between Region and season:

 

 

Spring

Summer

p-value

Region 1

.. %

 ..%

P1

Region 2

.. %

.. %

P2

Region 3

 ..%

.. %

P3

 

I want to:

Check if the % of people in region 1 is different between spring and summer (p-value or OR)

Check if the % of people in region 2 is different between spring and summer (p-value or OR)

Check if the % of people in region 3 is different between spring and summer (p-value or OR)

What test should I use to get the 3 p-values needed?

Respected Advisor
Posts: 3,061

Re: Analysis of a 2x2 Contingency Table

As far as I remember, a simple comparison of proportions as you describe (which is not really a 2x2 contingency table at all) is not programmed into any SAS PROC. However, it is simple enough to program in data step.

 

As is usual, @Rick_SAS has written up the explanation at https://blogs.sas.com/content/iml/2017/07/05/test-equality-two-proportions-sas.html

--
Paige Miller
Super User
Posts: 23,776

Re: Analysis of a 2x2 Contingency Table

It's not a 2X2 table, since it's literally a 1 (row=REGION) X 2 (column=SEASON) comparison. 

 

One way would be to use a BY statement in the PROC FREQ. 

 

Here's an example that gets the binomial test, which tests that the proportions should be 50% in each group. Note that you'll need the N's here, NOT the percentages. You need both the N and percentages or the raw data.

 

proc sort data=sashelp.class out=class; by age sex; run;

ods output binomialTest=pvalues;
proc freq data=class;
by age;
table sex / out=summary_table chisq binomial;
run;

PS. The reusults are not in a nice neat table, but all the information is in the two output tables:

  1. Summary_Table -> has the counts and percentages
  2. Values -> has the p-values for each test
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