Home » Topics » Nutrition and Anthropometry » not in the universe
| Re: not in the universe [message #15646 is a reply to message #15628] |
Mon, 27 August 2018 13:38   |
kingx025
Messages: 95
Registered: August 2016
Location: Minneapolis. Minnesota
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Senior Member |
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Brian Zetah, one of the grad RAs on the IPUMS-DHS project, checked the numbers and sorted out how various children end up in the NIU category for your samples of interest.
Some of the universes for the biometric variables in the KR file use wording such as: Ghana 2014: Surviving children under age 5 who were measured as household members and whose co-resident mothers were female survey respondents age 15-49.
There are some universe restrictions implicit in the term "who were measured as household members"--and you can see those restrictions if you look at the universe for the child biometric measures using household members as the unit of analysis (from the PR files).
For example, the universe for the child biometric variables in the PR (household member) files is: Ghana 2014: Household member age 6-59 months, in households selected for weight, height, and hemoglobin measurements.
So, children under 6 months were excluded, children who were dead were excluded, children who were not measured for some reason were excluded, and children in households NOT selected for weight, height, and hemoglobin measurements were excluded.
I reproduce, below, Brian's summary of his results, looking at the samples of interest for you, for more detail:
It seems like this user is not taking into account cases of women/children who were not selected for various reasons.
As shown in the picture the user attached, there are 35,495 cases that are NIU. 28,490 cases can be accounted for simply by the fact that their household was not selected for hemoglobin measurements.
We now have 7,005 cases where the household was selected for hemoglobin measurements, but are still NIU. To figure out these remaining cases, around half of these cases are due to the ages of these children. As noted in the universe, children under 6 months of age are excluded.
So now we have 3,646 cases left to account for. For these cases, I looked at hwwhynotmeas (hw13), which reports whether the child was measured and the reason why not if they weren't measured.
This also makes sense, as we wouldn't expect any data for dead children or children for whom no measurements were found. Thus, this user may find it helpful to drop all cases where hemoselect (v042) == 0, hwwhynotmeas (hw13) == 97 (no measurement found in household), and kidagemo (hw1) < 6 (children under 6 months).
This thread on the user forum may be also helpful in explaining cases of "no measurement found in household." Of particular interest is a comment from Trevor, where he notes:
"There are two parts to the explanation:
1) In DHS, we first interview households, collect a list of persons living in the household and who slept in the household the night before the survey, and for selected groups of these people (children under age 5, women age 15-49, sometimes men age 15-49/54/59) we collect anthropometric measures and biomarker information. When we interview women we also collect a history of all of the children the woman has given birth to. HW13 in the BR and KR files relates to all of the children the woman has given birth to, and some of these may not live in the household. Any living child of the woman interviewed who does not usually live in the household and did not sleep in the household the night before the survey will have no anthropometric information collected for them in the household/biomarker questionnaire and are coded "no measurement found in household".
2) For surveys such as Malawi 2010 and Mali 2012 the anthropometric and biomarker information collected in the survey was only collected in a portion of the sample. For Malawi 2010, see section 1.7 on page 5 of the Malawi DHS 2010 report which explains that the hemoglobin test was conducted in a sub-sample of one third of households only. For Mali DHS 2012, I believe that a subsample of half of the households was used (see Mali 2012-13 DHS report). You should select only the households that were selected for the anthropometry and biomarker data collection (v042 == 1).
Code: [Select all] [Show/ hide]
tab hw13 v042,m
to see the cases selected and not selected.
In general when analyzing the data on nutrition of children, we would recommend using the PR file and the HC series of variables which includes all children living in the household or who slept in the household the previous night and on which we base our analysis, rather than the BR or KR file. However, as it appears that you are linking this to intimate partner violence, there is no advantage to this as you need to be linking women and their children, but this also means that you will have no anthropometry or biomarker information for any child who does not live with the respondent, which would clearly be a limitation of your study (with a possible bias as it is possible that children not living with their mothers may be correlated with intimate partner violence)." (emphasis added)
As a side note, given Trevor's recommendation to use the PR file, it may be helpful to direct this user to use household members as the unit of analysis on the IPUMS-DHS site.
That's the end of Brian's summary. I will work with the IPUMS-DHS team to make sure that the full detail on universes for the child biometric variables is consistently included.
Thanks for drawing our attention to this issue.
Miriam King
Dr. Miriam King
IPUMS-DHS Project Manager (www.idhsdata.org)
[Updated on: Mon, 27 August 2018 13:46] Report message to a moderator |
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