Date:         Tue, 6 Nov 2007 09:45:24 -0800
Reply-To:     King Douglas <king_d@swbell.net>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         King Douglas <king_d@swbell.net>
Subject:      Re: Randomization into 3 groups
Comments: To: "Parise, Carol A." <PariseC@sutterhealth.org>
In-Reply-To:  <5E0F889A8147254F83D0250D0E7CE6C66C130D@DCSH15VX.root.sutterhealth.org>
Content-Type: text/plain; charset=iso-8859-1

Carol,

Here are two nifty solutions, one provided by Jan Spousta, the other by Raynald Levesque and both posted to this list just a few weeks ago.

I'm sure that either will prove useful, given slight modifications.

Regards,

King Douglas
American Airlines Customer Research

http://www.kingdouglas.com/SPSS.HTM


JAN SPOUSTA:

 Run the following syntax from a Syntax window (Run -> All) ; suppose you have opened a datafile with 96 rows:

 COMPUTE aux_id = $casenum /*to be able to restore the original order of rows*/.
 COMPUTE random_number = uniform(1) .
 SORT CASES BY random_number (A) .
 compute random_number = $casenum /*to convert the random numbers from <0,1> into 1, 2, 3..., N */.
 compute random_group = mod(random_number, 3) + 1 /* create 3 groups */.
 SORT CASES BY aux_id (A) .
 formats random_group aux_id random_number (f6).
 var lab random_group "Random group".

 Results are in the variable random_group. Hope this helps

 Jan

RAYNALD LEVESQUE:

 Here is one method:

 * Create a sample file for illustration purspoes.
 INPUT PROGRAM.
 LOOP id=1 TO 96 .
 - END CASE.
 END LOOP .
 END FILE.
 END INPUT PROGRAM.

 * Do the job.
 COMPUTE draw=UNIFORM(1).
 SORT CASES BY draw.
 RANK VARIABLES=draw /NTILES(3) INTO group .

 Regards

 --
 Raynald Levesque
 www.spsstools.net

"Parise, Carol A." <PariseC@sutterhealth.org> wrote: Hi all,

Does anyone have some nifty code to tell SPSS to do the following:

1. Create a variable called ID and assign ID numbers 1-315.
2. Create a variable called Group and randomly assign a 1, 2, or 3 to each of the 315 IDs so that 105 cases get a 1, 105, get a 2 and 105 get a 3.

I've used UNIFORM to randomly assign a list to either a 1 or 0 and i could easily create these variables and mannually do this.

However, seeing the syntax to do this would be valuable for some other tasks like this.

Thanks
Carol

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