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From | Arturo Rodriguez <arturo.rdgz.trejo@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: Probability and non-response weights; how can I create a composite weight? |
Date | Fri, 18 Nov 2011 15:13:37 -0600 |
Hi everybody, I am working with survey data which was collected through a one-stage cluster sample with stratification (i.e. health clinics in a region were selected to be part of the study first and then villages surrounding those clinics were randomly sampled, all households in the selected villages and all women in those households were then surveyed). My question is regarding the proper use of a composite design weight. Here are the details: (1) DESIGN WEIGHTS I have calculated probability weights for each h_th stratum ... (i.e. pw = total_villages_h / sampled_villages_h) I have also calculated unit non-response weights for each h_th stratum ... (i.e. unrw = total_eligible_households_h / sampled_households_h) I then created a composite weights (sw) by multiplying pw * unrw = sw and used the following command to define my survey data: svyset village_number [pweight = sw], strata(clinic) fpc(total_villages_h) I have read that using a composite weight (sw = pw*unrw) is not recommended and that I should weight my sample first by pw and then weight again by unrw. My first question is: Can STATA do this automatically? How? If not, do I have to multiply each of my 300+ variables by pw and then by unrw? What is the most efficient way to do this? I asked STATA to calculate estimated population totals for each of the areas surrounding the clinics but I am getting figures that are very low compared to what is known to be true. Is there anything I can do to correct this statistically? Or is it just that my sample is not representative? (2) POST-STRATIFICATION WEIGHTS Will adding poststrata and postweight to my svyset make any difference in obtaining better "population around clinic" point estimates? Or will it only change my STD ERRORS? Thanks in advance for all the wisdom. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/