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Date:         Wed, 16 Jan 2008 03:34:19 -0500
Reply-To:     Richard Ristow <>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
Comments:     RFC822 error: <W> MESSAGE-ID field duplicated. Last occurrence
              was retained.
From:         Richard Ristow <>
Subject:      Re: drawing samples for hundreds of workers
Comments: To: "Raffe, Sydelle, SSA" <>
Comments: cc: King Douglas <>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 08:33 PM 1/14/2008, Raffe, Sydelle, SSA wrote:

>In my file, there are unique case records. These are apportioned to >hundreds of different workers such that each worker has multiple cases. > >We want to make a random selection of each workers cases. I don't >think that's what I led [John Norton] to understand.

And at 01:40 PM 1/15/2008, Raffe, Sydelle, SSA wrote:

>Actually, we want 6 cases randomly selected for each worker.

King Douglas gave a nice implementation using SORT CASES and RANK. As an alternative, here's the implementation with AGGREGATE and 'k/n' logic. (It requires that the file be grouped, but not necessarily sorted, by ID.) I'm selecting three records per worker.

|-----------------------------|---------------------------| |Output Created |16-JAN-2008 03:32:16 | |-----------------------------|---------------------------| ID Fname Lname RecdDate

A35 Aaron Aardvark 18-DEC-2004 A35 Aaron Aardvark 25-MAY-2005 A35 Aaron Aardvark 16-JUL-2005 A42 Bethany Birkinwell 30-OCT-2004 A42 Bethany Birkinwell 05-DEC-2004 A42 Bethany Birkinwell 24-DEC-2004 A42 Bethany Birkinwell 25-DEC-2004 C19 Charles Cubbage 25-JUL-2003 C19 Charles Cubbage 02-SEP-2003 C21 Dorothy Dickens 14-NOV-2002 D98 Ellis Etheridge 19-SEP-2000

Number of cases read: 11 Number of cases listed: 11

AGGREGATE OUTFILE=* MODE=ADDVARIABLES /BREAK=ID /NRecords 'Number of records for employee'=NU.


DO IF $CASENUM EQ 1 OR ID NE LAG(ID). . COMPUTE #N = NRecords /* Total records, per worker */. . COMPUTE #K = MIN(3,#N) /* Number to sample, per worker */. END IF.

. /*-- PRINT / 'Record ' ID Fname Lname RecdDate ': ' /*-*/ /*-- 'K=' #K ', N=' #N /*-*/.

COMPUTE #Take_It = RV.BERNOULLI(#K/#N). COMPUTE #K = #K - #Take_It. COMPUTE #N = #N - 1.

. /*-- PRINT / ' TAKE=' #Take_It /*-*/.


. /*-- EXECUTE /*-*/.


List |-----------------------------|---------------------------| |Output Created |16-JAN-2008 03:32:17 | |-----------------------------|---------------------------| ID Fname Lname RecdDate NRecords

A35 Aaron Aardvark 18-DEC-2004 3 A35 Aaron Aardvark 25-MAY-2005 3 A35 Aaron Aardvark 16-JUL-2005 3 A42 Bethany Birkinwell 30-OCT-2004 4 A42 Bethany Birkinwell 05-DEC-2004 4 A42 Bethany Birkinwell 25-DEC-2004 4 C19 Charles Cubbage 25-JUL-2003 2 C19 Charles Cubbage 02-SEP-2003 2 C21 Dorothy Dickens 14-NOV-2002 1 D98 Ellis Etheridge 19-SEP-2000 1

Number of cases read: 10 Number of cases listed: 10 =================== APPENDIX: Test data =================== * ................................................................. . * ................. Test data ..................... . SET RNG = MT /* 'Mersenne twister' random number generator */ . SET MTINDEX = 3605 /* Providence, RI telephone book */ .

INPUT PROGRAM. . DATA LIST LIST /ID Fname Lname (A4,A8, A12). . LEAVE ID Fname Lname. . NUMERIC RecdDate (DATE11). . LEAVE RecdDate. . COMPUTE RecdDate=RV.UNIFORM(DATE.MDY(01,01,2000), DATE.MDY(01,01,2005)). . COMPUTE RecdDate=XDATE.DATE(RecdDate).

. NUMERIC #NRecrds #RecdNum (F3). . COMPUTE #NRecrds = TRUNC(RV.UNIFORM(1,5)). . LOOP #RecdNum = 1 TO #NRecrds. . COMPUTE RecdDate = RecdDate + RV.EXP(1/TIME.DAYS(45)). . COMPUTE RecdDate=XDATE.DATE(RecdDate). . END CASE. . END LOOP. END INPUT PROGRAM.

BEGIN DATA A35 Aaron Aardvark A42 Bethany Birkinwell C19 Charles Cubbage C21 Dorothy Dickens D98 Ellis Etheridge END DATA.


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