| Trend analysis with different number of 'PSU' and 'Strata' [message #24160] |
Mon, 07 March 2022 06:59  |
Mason92
Messages: 33
Registered: December 2021
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Member |
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I plan to do trend analysis for some indices using two Pakistan DHSs conducted in 2012-13 and 2017-18. The sampling frame of PDHS 2017-18 was based on the 2017 census which included the population of AJK and FATA areas. While the PDHS 2012-13 was based on 1998 census; the PDHS 2012-13 did not include the AJK and FATA areas.
Secondly, the PDHS 2017-18 has 580 PSUs and 16 strata, while the PDHS 2012-13 has 500 PSUs and 10 strata. Would it be statistically okay to append both data files and conduct trend analysis?
Kindly guide!
Thank you.
[Updated on: Mon, 07 March 2022 06:59] Report message to a moderator |
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| Re: Trend analysis with different number of 'PSU' and 'Strata' [message #24164 is a reply to message #24160] |
Mon, 07 March 2022 10:45  |
Bridgette-DHS
Messages: 3199
Registered: February 2013
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Senior Member |
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Following is a response from DHS Lead Statistician, Ruilin Ren:
The Pakistan surveys are not easily combined because of their differences. First, you cannot simply append the two surveys data because of the normalization of the sampling weight, especially with the different coverage and different normalization polices. The 2012-13 survey did not include AJK and FATA regions, but the two regions are small, they together represent only about 5% of Pakistan. Second, the 2017-18 survey had a separate normalization policy, requested by the Government of Pakistan. GB and AJK were normalized separately and independently. If you want to use the 2017-18 survey data for all Pakistan, the denormalization of must be done in 3 parts, separately for GB, AJK, and the rest of Pakistan. We cannot help with that.
The recommendation is that you analyze trends using just the areas that were included in both the surveys. You can append the data files but note that the PSUs (clusters) in the two surveys were different.
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| Re: Trend analysis with different number of 'PSU' and 'Strata' [message #24166 is a reply to message #24164] |
Mon, 07 March 2022 15:38 |
Mason92
Messages: 33
Registered: December 2021
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Member |
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Thank you so much for the prompt and very clear guidance, I am very grateful.
So, using the appended datafile, would it be correct to look at trends by looking at each province/region individually (or two provinces/regions combined) that were collected in both surveys by using the Stata commands:
. svy: logit i.sample d105a if v024 == 1
. svy: logit i.sample d105a if v024 == 1 2
* The newly created variable in the appended file "sample" will be coded as 0 if data from PDHS 2012-13, and 1 if data from PDHS 2017-18
* Variable v024 to be recoded as binary (0/1)
Finally, would it be statistically correct to analyze trends even if, for the same province/region, the number of clusters is different in the two surveys? Is there any rule-of-thumb when the number of clusters is different in two surveys?
Thank you.
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