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A random sample in SAS is selected by using the SAS samplerand procedure. This procedure randomly selects observations from a dataset and can be used with a variety of parameters to create a sample that best suits the needs of the researcher. Examples of this procedure can be found in the SAS documentation, which includes examples of sampling from a single dataset, multiple datasets, and stratified samples.
Here are the two most common ways to select a of rows from a dataset in SAS:
Method 1: Select Random Sample Using Sample Size
proc surveyselect data=original_data
out=random_sample
method=srs /*specify simple random sampling as sampling method*/
sampsize=3 /*select 3 observations randomly*/
seed=123; /*set seed to make this example reproducible*/
run;
Method 2: Select Random Sample Using Proportion of Total Observations
proc surveyselect data=original_data
out=random_sample
method=srs /*specify simple random sampling as sampling method*/
samprate=0.2 /*select 20% of all observations randomly*/
seed=123; /*set seed to make this example reproducible*/
run;
The following examples show how to use each method with the following dataset in SAS:
/*create dataset*/
data original_data;
input team $ points rebounds;
datalines;
Warriors 25 8
Wizards 18 12
Rockets 22 6
Celtics 24 11
Thunder 27 14
Spurs 33 19
Nets 31 20
Mavericks 34 10
Kings 22 11
Pelicans 39 23
;
run;
/*view dataset*/
proc print data=original_data;
Example 1: Select Random Sample Using Sample Size
The following code shows how to select a random sample of observations from the dataset using a sample size of n=3:
/*select random sample*/
proc surveyselect data=original_data
out=random_sample
method=srs
sampsize=3
seed=123;
run;
/*view random sample*/
proc print data=random_sample;
We can see that three rows were randomly selected from the original dataset.
Example 2: Select Random Sample Using Proportion of Total Observations
The following code shows how to select a random sample of observations from the dataset by using the samprate function to specify that we’d like the random sample to represent 20% of all original observations:
/*select random sample*/
proc surveyselect data=original_data
out=random_sample
method=srs
samprate=0.2
seed=123;
run;
/*view random sample*/
proc print data=random_sample;
The following tutorials explain how to perform other common tasks in SAS: