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Date:         Fri, 7 Jul 2006 13:23:16 -0500
Reply-To:     "Reutter, Alex" <areutter@spss.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Reutter, Alex" <areutter@spss.com>
Subject:      Re: PPS sampling
Content-Type: text/plain; charset="US-ASCII"

Using the CSPLAN and CSSELECT procedures in the Complex Samples option is a fairly painless way to handle this in SPSS. If I correctly understand what you want to do, you will need a "measure of size" variable. For example:

Case/Pupil School SchoolSize 1 1 116 2 1 116 ... 116 1 116 117 2 163 118 2 163 ...

Then work through the Sampling Wizard. You should end up with something like:

CSPLAN SAMPLE /PLAN FILE='mysample.csplan' /METHOD TYPE=PPS_SYSTEMATIC /MOS VARIABLE= SchoolSize /RATE VALUE=0.25. CSSELECT /PLAN FILE='mysample.csplan'.

The sampling plan is defined by CSPLAN (systematic sampling of 1/4 pupils with probability proportional to school size) and the specifications are saved to the external file mysample.csplan. CSSELECT uses the information in this file to carry out the actual sampling. Analysis procedures in the Complex Samples option use the information this file to ensure correct computation of statistics according to the complex sampling plan.

Cheers, Alex

> -----Original Message----- > From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of > Cathal McCrory > Sent: Friday, July 07, 2006 10:06 AM > To: SPSSX-L@LISTSERV.UGA.EDU > Subject: PPS sampling > > I have the enrolment numbers for 3200 schools and I want to select 13,000 > pupils from within these schools on a PPS basis. For example: > > Pupil Cumulative > School Enrolment Population > 1 116 116 > 2 163 279 > 3 232 511 > 4 204 715 > 5 274 989 > 6 188 1177 > 7 210 1387 > 8 407 1794 > 9 298 2092 > > I want to generate a random start within SPSS and select every 4th pupil > from within the cumulative population total (rather than a set number of > cases) and have the program iterate until I have drawn my sample of > 13,000. > I was wondering whether anyone could give me any pointers (to existing > routines) or offer any guidance on this. Many thanks. >


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