I believe there is an error in the programming of the Complex Samples (CS) module of SPSS version 22. I copy below the syntax used to generate a two-stage probability proportional to size (PPS) cluster sample design and selection plan for a population with nine clusters of varying size described in the table below. The design selects 3 clusters out of 9 with PPS:
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Cluster
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1
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2
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3
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4
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5
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6
|
7
|
8
|
9
|
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Households
|
20
|
100
|
50
|
15
|
18
|
43
|
20
|
36
|
13
|
The syntax program I ran is as follows:
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* Asistente de muestreo.
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CSPLAN SAMPLE
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/PLAN FILE='C:\Users\gaine\Documents\apgea\mis_cursos_ceadcs_pipe\Cohorte '+
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'2022-2023\16_muestreo_para_investigadores_2022\04_clases_modalidad_virtual\tema_07_preparacion'+
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'\00_apoyos\spss\prueba.csplan'
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/PLANVARS SAMPLEWEIGHT=SampleWeight_Final_
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/PRINT PLAN
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/DESIGN STAGELABEL='1' CLUSTER=Manzana
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/METHOD TYPE=PPS_SAMPFORD ESTIMATION=DEFAULT
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/MOS VARIABLE=Vivienda
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/SIZE VALUE=3
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/STAGEVARS INCLPROB(InclusionProbability_1_) CUMWEIGHT(SampleWeightCumulative_1_)
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POPSIZE(PopulationSize_1_) SAMPSIZE(SampleSize_1_) RATE(SamplingRate_1_) WEIGHT(SampleWeight_1_)
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/DESIGN STAGELABEL='2'
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/METHOD TYPE=SIMPLE_WOR
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/SIZE VALUE=7
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/STAGEVARS INCLPROB(InclusionProbability_2_) CUMWEIGHT(SampleWeightCumulative_2_)
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POPSIZE(PopulationSize_2_) SAMPSIZE(SampleSize_2_) RATE(SamplingRate_2_) WEIGHT(SampleWeight_2_).
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CSSELECT
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/PLAN FILE='C:\Users\gaine\Documents\apgea\mis_cursos_ceadcs_pipe\Cohorte '+
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'2022-2023\16_muestreo_para_investigadores_2022\04_clases_modalidad_virtual\tema_07_preparacion'+
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'\00_apoyos\spss\prueba.csplan'
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/CRITERIA STAGES=1 2 SEED=1
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/CLASSMISSING EXCLUDE
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/SAMPLEFILE OUTFILE='C:\Users\gaine\Documents\apgea\mis_cursos_ceadcs_pipe\Cohorte '+
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'2022-2023\16_muestreo_para_investigadores_2022\04_clases_modalidad_virtual\tema_07_preparacion'+
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'\00_apoyos\spss\prueba.sav'
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/JOINTPROB OUTFILE='C:\Users\gaine\Documents\apgea\mis_cursos_ceadcs_pipe\Cohorte '+
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'2022-2023\16_muestreo_para_investigadores_2022\04_clases_modalidad_virtual\tema_07_preparacion'+
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'\00_apoyos\spss\proba.sav'
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/PRINT SELECTION.
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The sample selected by CS from SPSS contains selection probabilities in the first stage that instead of varying with cluster size are all equal to 0.33. The values that should have been included as first-stage selection probabilities are:
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PPS first stage
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0,19
|
0,95
|
0,48
|
0,14
|
0,17
|
0,41
|
0,19
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0,34
|
0,12
|
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SPSS
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0,33
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0,33
|
0,33
|
0,33
|
0,33
|
0,33
|
0,33
|
0,33
|
0,33
|
The SPSS CS manual does not help to know what might be going on. Perhaps I am wrong and precisely for that reason I am posting it.
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Alberto Camardiel
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