Date: Wed, 28 Sep 2005 10:31:23 -0400
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Art Kendall <Art@DrKendall.org>
Organization: Social Research Consultants
Subject: Re: complex samples
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If you do not use the complex samples module, given that all of the
design factors are stratifications (fixed effects), the error estimates
(confidence intervals) for the whole pop will be wider than necessary.
If the obtained intervals using the base are sufficiently narrow that
you can live with them, then you might forego using the complex
samples. If you intend to compare and contrast sets of cells, then you
would be better off using the smaller error terms from complex samples.
"The size of the sample is partly
based on cost considerations, logistics etc."
How are you gathering your data? By interview of by paper-and-pencil reports by the schools?
Keep in mind that the total cost of a survey is NOT a simple direct effect of the sample size, especially in phone or mail surveys. A great deal of the cost is in instrument development, results reporting, etc.
"The NGO claims that dividing the
schools into strata means that the sample is more likely to be
representative as you can ensure that each of the strata is represented
proportionally within the sample."
Proportional representation is important for ease in calculation of precision of pop estimates. It also helps plausibility of the design. For comparing and contrasting strata etc., equal cell sizes yield smaller error estimates.
Social Research Consultants
University Park, MD USA Inside the Washington, DC beltway.
>I am asking this question on behalf of an NGO that surveys primary
>schools. They look at service delivery issues, leakage of funding,
>corruption etc. From approximately 5000 primary schools, the sampling
>frame is ten per cent (or 500 schools). The size of the sample is partly
>based on cost considerations, logistics etc. The 500 schools were
>selected through a random, 2 stage probability proportionate to size
>selection process based on the number of schools. The schools were
>divided according to regions: Northern region, Central Region and
>Southern region. Then the schools in the region were further divided
>into rural and urban schools. Finally, the schools were proportionally
>selected through random sampling. The NGO claims that dividing the
>schools into strata means that the sample is more likely to be
>representative as you can ensure that each of the strata is represented
>proportionally within the sample.
>Does analysis of this data require the complex samples module in SPSS?
>Any thoughts are appreciated,