I'm using Stata 8.2 and have a question about the use of fpc with
systematic sampling. As I understand it, fpc is for use with simple random
sampling without replacement, especially when the sampling fractions are
fairly large. In my case, I have complex data in which clusters were
randomly selected within strata using systematic sampling using a random
start number and sampling interval.
The within-strata cluster sampling fractions are fairly high in my sample,
ranging from 16-44%, and using the fpc option actually reduces the
variance in my model so that several variables achieve significance
compared to when fpc is not used. I don't know if this is appropriate,
however.
In short, I realize fpc would be appropriate if the clusters were selected
by pure simple random sampling w/o replacement. My question, then, is
this: Is it appropriate to use the fpc option when clusters were sampled
using systematic random sampling (presumably w/o replacement)?
Thank you,
Eric Sevigny
University of Pittsburgh
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