Fisher’s exact test is a statistical test used to determine if there are nonrandom associations between two categorical variables.In SAS this is carried out using PROC FREQ. We use the Tables option to use the two variables subjected to Fisher Exact test.

Syntax

The basic syntax for applying Fisher Exact test in SAS is −

PROC FREQ DATA = dataset ;
TABLES Variable_1*Variable_2 / fisher;

Following is the description of the parameters used −

• dataset is the name of the dataset.

• Variable_1*Variable_2 are the variables form the dataset .

Applying Fisher Exact Test

To apply Fisher’s Exact Test, we choose two categorical variables named Test1 and Test2 and their result.We use PROC FREQ to apply the test shown below.

Example

data temp;
input Test1 Test2 Result @@;
datalines;
1 1 3 1 2 1 2 1 1 2 2 3
;

proc freq;
tables Test1*Test2 / fisher;
run;

When the above code is executed, we get the following result −

sas 4

SAS – Repeated Measure Analysis

Repeated measure analysis is used when all members of a random sample are measured under a number of different conditions. As the sample is exposed to each condition in turn, the measurement of the dependent variable is repeated. Using a standard ANOVA in this case is not appropriate because it fails to model the correlation between the repeated measures.

One should be clear about the difference between a repeated measures design and a simple multivariate design. For both, sample members are measured on several occasions, or trials, but in the repeated measures design, each trial represents the measurement of the same characteristic under a different condition.

In SAS PROC GLM is used to carry out repeated measure analysis.

Syntax

The basic syntax for PROC GLM in SAS is −

PROC GLM DATA = dataset;

CLASS variable;

MODEL variables = group / NOUNI;

REPEATED TRIAL n;

Following is the description of the parameters used −

• dataset is the name of the dataset.

• CLASS gives the variables the variable used as classification variable.

• MODEL defines the model to be fit using certain variables form the dataset.

• REPEATED defines the number of repeated measures of each group to test the hypothesis.

Example

Consider the example below in which we have two groups of people subjected to test of effect of a drug. The reaction time of each person is recorded for each of the four drug types tested. Here 5 trials are done for each group of people to see the strength of correlation between the effect of the four drug types.

DATA temp;

INPUT person group $ r1 r2 r3 r4;

CARDS;

1 A 2 1 6 5

2 A 5 4 11 9

3 A 6 14 12 10

4 A 2 4 5 8

5 A 0 5 10 9

6 B 9 11 16 13

7 B 12 4 13 14

8 B 15 9 13 8

9 B 6 8 12 5

10 B 5 7 11 9

;

RUN;

PROC PRINT DATA = temp ;

RUN;

PROC GLM DATA = temp;

CLASS group;

MODEL r1-r4 = group / NOUNI ;

REPEATED trial 5;

RUN;

When the above code is executed, we get the following result −

sas 5

So, this brings us to the end of blog. This Tecklearn ‘Fishers Exact Tests and Repeated Measure Analysis in SAS’ blog helps you with commonly asked questions if you are looking out for a job in SAS. If you wish to learn SAS and build a career in Data Analytics domain, then check out our interactive, SAS Training for SAS BASE Certification Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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• SET Statement

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