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From |
Ameya Bondre <ameyabondre.jhsph@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: appending two survey data sets |

Date |
Wed, 31 Oct 2012 15:13:06 -0700 |

My name is Ameya Bondre and I am working on two survey data sets for a sustainability study, and had few questions. The study design: To give you a background - I have to compare a range of conditions (health behaviors, diseases and health services) in a region, at the end of a health program (year 2009 - endline survey), with similar conditions two years after the program stopped (year 2011 - evaluation survey, to measure sustainability of program activities). I have two data sets for the two cross-sectional surveys conducted in 2009 and 2011. The surveys are independent (as in, the sampling was done again in 2011). The populations surveyed each time, are different cross-sections of the same region. Both surveys involve the same sampling technique with "block" as the stratum, "health center" as the primary sampling unit and "respondents/mothers" as the secondary sampling unit (but the variable names for these design variables are different in 2009 and 2011 data sets). I am using STATA 10. No FPC correction has been applied as per the program reports. Questions (sampling weights and svy command): 1) I have probability weights already given in the 2009 data sets but I don't have those built in, for the 2011 data sets. I have been told that the entire sampling method was similar for both years. Am I understanding correctly that I first need to calculate weights for all observations for 2011, then append data sets, and then set up the combined data set as a "survey set"? 2) Further, do I need to create the sampling weight variable by calculating probability weights for 2011 observations (which I already have for 2009) ? if yes, what's the method to get weights - would I require the region's population (N) in 2011? 3) Do I need to create new design variables for the svyset command, after appending the two data sets? (like one variable for psu, strata, weight - taking both data sets into account) Questions (appending data sets) 4) In appending, I am not able to label the variables/observations for 2011 separately from 2009, to identify them as "2009" and "2011" variables (as appending adds observations and I want to compare trends across both years), how do I do that? 4) Since I am using STATA 10 with limited memory and my data sets are huge (800 odd variables and sample sizes in thousands); can I append few variables at a time (that I need to analyze, for certain regressions), instead of the entire data set - would that affect the survey design of the new combined data set, after appending? Please do let me know if any question is not clear. Thanks for your time.. Best, Ameya Bondre * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: appending two survey data sets***From:*Stas Kolenikov <skolenik@gmail.com>

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