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Re: Where can I find z-scores? [message #2548 is a reply to message #2546] Thu, 10 July 2014 13:20 Go to previous messageGo to previous message
Trevor-DHS is currently offline  Trevor-DHS
Messages: 800
Registered: January 2013
Senior Member
Hi Giacomo,

A couple of notes for you:
1) You don't need to compute the z-scores for older rounds of data. The Z-scores for the older rounds of surveys are available in separate data files that can be downloaded. These are the HW (Height and Weight scores) files, for example for Benin 2001 the file is BJHW41xx.zip (where xx is the type of data file).
2) The reason you are not matching the z-scores in the DHS data is because of the calculation of age used in the computation of the Z-scores. HW1 only gives age rounded off to the month, but in the calculation of the z-scores we compute age to the day, as follows:

* Calculate measurement date in days
gen mdate = mdy(hw18, hw17, hw19)
* Calculate birth date in days
gen bdate = mdy(b1, hw16, b2) if hw16 <= 31
replace bdate = mdy(b1, 15, b2) if hw16 > 31
* Calculate age in months with days expressed as decimals.
gen age = (mdate-bdate)/30.4375
* Compute Z-scores
zscore06, a(age) s(b4) h(hw3_2) w(hw2_2)

Note, though that the zscore06 software does not handle some of the flagging of data that we do, so you will find some differences related to flagged cases and to cases where the data of birth was imputed (where b10 != 1).

I hope this helps.
 
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