24760 - Stratified random sample without replacement, equal allocation

Sample 24760: Stratified random sample without replacement, equal allocation

/* Create sample data base of student grade point averages from           */
/* East High School, Grades 9 through 12, 100 or more students per grade. */

data EastHigh;
  format GPA 3.1;
  do Grade=9 to 12;
    do StudentID=1 to 100+int(201*ranuni(432098));
      GPA=2.0 + (2.1*ranuni(34280));
      output;
    end;
  end;
run;


/* Method 1: Using PROC SURVEYSELECT                          */
/*                                                            */
/* N= is the number of observations to select from            */
/* each group.  Use METHOD=SRS.  The statement STRATA defines */
/* the variable that is used for grouping.  OUT= names the    */
/* SAS data set that will be created by the procedure.        */

proc surveyselect data=EastHigh method=srs n=5 out=sample;
  strata Grade;
run;

title 'Method 1: PROC SURVEYSELECT';
proc print data=sample;
run;



/* Method 2: Using Base SAS                                                  */
/*                                                                           */
/* Generate a random number for each observation in the data set.            */
/* Sort the data set adding the new variable to the end of the BY statement. */
/* This will randomly order observations within the BY-Group. In the next    */
/* DATA step, reset a counter every time the sampling group changes. Output  */
/* the number of observations that you want in each sample group.            */

data temp; 
  set EastHigh; 
  abc=ranuni(15243); 
run; 

proc sort data=temp; 
  by grade abc; 
run;
 
data sample; 
  set temp; 
  by grade; 
  if first.grade then count=0; 
  count+1; 
  if count <=5 then output; 
  drop count abc; 
run;
 
title "Method 2: Using BASE SAS with sort on random variable ";
proc print data=sample; 
run; 



/* Method 3: Using Base SAS, no extra sort required            */
/*                                                             */
/* Since the process involves choosing a small sample from     */
/* each of the subgroups of the data to make the entire random */
/* sample, you need to do the following:                       */
/* - count the observations in each category                   */
/* - sort the observations into categories                     */
/* - combine the sorted data set with the category counts      */
/* - select the observations for the sample.                   */

/*  Use PROC FREQ to count the number of observations in each  */
/*  category.                                                  */

proc freq data=EastHigh;
  tables grade / out=bycount noprint;
run;


/* Combine the data sets by GRADE */

data sample(drop=k count);
  merge EastHigh bycount(drop=percent);
  by Grade;

  /*  Use a RETAIN statement to create a variable that will contain */
  /*  the number of observations that you want from each category.  */
  /*  Initialize the new variable to that number each time the      */
  /*  category changes by testing FIRST.GRADE.                      */

  retain k;
  if first.grade then k=5;

  /*  COUNT, the number of observations in each category, comes from */
  /*  the PROC FREQ step.  Decrease COUNT by 1 on each iteration of  */
  /*  the DATA step to reflect the number of observations remaining  */
  /*  in the group.                                                  */

  if ranuni(15243)<=k/count then do;
    output;
    k=k-1;
    end;
  count=count-1;
run;

title "Method 3: Using BASE SAS with no extra sort on random variable ";
proc print data=sample;
run;

These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.

Method 1: PROC SURVEYSELECT                                                                                                14:27 Thursday, November 4, 2004  61

                       Student    Selection    Sampling
Obs    Grade    GPA       ID         Prob       Weight

  1       9     2.4       17       0.017123      58.4
  2       9     2.9       19       0.017123      58.4
  3       9     3.4       66       0.017123      58.4
  4       9     3.4      141       0.017123      58.4
  5       9     3.5      291       0.017123      58.4
  6      10     3.6       15       0.041667      24.0
  7      10     3.7       21       0.041667      24.0
  8      10     2.1       32       0.041667      24.0
  9      10     3.5       92       0.041667      24.0
 10      10     2.8      119       0.041667      24.0
 11      11     2.2       24       0.030120      33.2
 12      11     3.1       63       0.030120      33.2
 13      11     3.5       90       0.030120      33.2
 14      11     3.0       96       0.030120      33.2
 15      11     2.8      139       0.030120      33.2
 16      12     2.2        6       0.022422      44.6
 17      12     3.5       23       0.022422      44.6
 18      12     3.4       25       0.022422      44.6
 19      12     3.1       68       0.022422      44.6
 20      12     2.1      114       0.022422      44.6




Method 2: Using BASE SAS with sort on random variable                                                                      14:27 Thursday, November 4, 2004  62

                       Student
Obs    GPA    Grade       ID

  1    3.0       9       144
  2    3.7       9        81
  3    2.6       9         9
  4    3.3       9        39
  5    3.3       9         4
  6    2.6      10        11
  7    4.1      10       102
  8    3.6      10        28
  9    2.8      10       108
 10    2.6      10        20
 11    2.7      11        98
 12    3.4      11        91
 13    2.2      11        49
 14    2.1      11        50
 15    3.3      11        97
 16    2.3      12        75
 17    4.0      12         9
 18    4.1      12       195
 19    3.0      12       148
 20    3.3      12        80




Method 3: Using BASE SAS with no extra sort on random variable                                                             14:27 Thursday, November 4, 2004  63

                       Student
Obs    GPA    Grade       ID

  1    3.3       9         4
  2    2.6       9         9
  3    3.3       9        39
  4    3.0       9       144
  5    2.5       9       290
  6    2.6      10        11
  7    2.6      10        20
  8    3.6      10        28
  9    4.1      10       102
 10    2.8      10       108
 11    3.7      11        45
 12    2.2      11        49
 13    3.4      11        91
 14    2.7      11        98
 15    3.1      11       165
 16    2.8      12         7
 17    4.0      12         9
 18    4.1      12        38
 19    2.3      12        75
 20    3.0      12       148

Select a specific number of observations from different groups, where no observation can be chosen more than once.

Type:	Sample
Topic:	Analytics ==> Survey Sampling and Analysis SAS Reference ==> Procedures ==> SURVEYSELECT SAS Reference ==> DATA Step

Date Modified:	2016-01-11 16:03:45
Date Created:	2004-09-30 14:09:11

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		OpenVMS VAX
		Microsoft® Windows® for 64-Bit Itanium-based Systems
		Microsoft Windows Server 2003 Datacenter 64-bit Edition
		Microsoft Windows Server 2003 Enterprise 64-bit Edition
		Microsoft Windows XP 64-bit Edition
		Microsoft® Windows® for x64
		OS/2
		Microsoft Windows 8 Enterprise 32-bit
		Microsoft Windows 8 Enterprise x64
		Microsoft Windows 8 Pro 32-bit
		Microsoft Windows 8 Pro x64
		Microsoft Windows 8.1 Enterprise 32-bit
		Microsoft Windows 8.1 Enterprise x64
		Microsoft Windows 8.1 Pro
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		Microsoft Windows 10
		Microsoft Windows 95/98
		Microsoft Windows 2000 Advanced Server
		Microsoft Windows 2000 Datacenter Server
		Microsoft Windows 2000 Server
		Microsoft Windows 2000 Professional
		Microsoft Windows NT Workstation
		Microsoft Windows Server 2003 Datacenter Edition
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		Microsoft Windows Server 2012 R2 Std
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		Microsoft Windows XP Professional
		Windows 7 Enterprise 32 bit
		Windows 7 Enterprise x64
		Windows 7 Home Premium 32 bit
		Windows 7 Home Premium x64
		Windows 7 Professional 32 bit
		Windows 7 Professional x64
		Windows 7 Ultimate 32 bit
		Windows 7 Ultimate x64
		Windows Millennium Edition (Me)
		Windows Vista
		Windows Vista for x64
		64-bit Enabled AIX
		64-bit Enabled HP-UX
		64-bit Enabled Solaris
		ABI+ for Intel Architecture
		AIX
		HP-UX
		HP-UX IPF
		IRIX
		Linux
		Linux for x64
		Linux on Itanium
		OpenVMS Alpha
		OpenVMS on HP Integrity
		Solaris
		Solaris for x64
		Tru64 UNIX

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Sample 24760: Stratified random sample without replacement, equal allocation

Operating System and Release Information