Conducting Surveys on Disability: A Comprehensive Toolkit

on CSO population database 2003-2004 the sampling method
for the next stage was established.
The number of households that would be needed was
determined on the estimations of the CSO population database
in order to obtain our sample size for persons with disability.
Keeping in mind that the cluster effect is maximal with 30
households within the cluster, this would require doing a total
of 5000 to 6000 households.
The Second Stage of Sampling:
Choosing the Clusters
The sampling for the NDSA was carried out with a random selection
method. As data was available only for 30 provinces out of 34
regarding population figures, 2 different methods were used:
• One for the 30 provinces for which we had the
population pre-census;
• The other for the 4 provinces for which the population
pre-census data is not available. For these provinces the
sampling level was defined according to district-level
estimations and the sampling interval was different.
The province wise-estimates for population, using the Central
Statistics Office projections for 2003-2004, are available at
this level for the 4 provinces. From this list clusters, for the
4 provinces for which this information was not available in
the pre-census, the sampling was done using a separate
methodology.
For the particular case of the new provinces, Panjsheer and
Daikundi, which were initially part of other provinces Parwan
and Uruzgan respectively, there was representation for
the population because these provinces were part of other
provinces. The use of the PPS method ensured that we included
these provinces in the sample selection.
A sample of 150 clusters was defined, with a requirement for
over-sampling, which came to a total of 175 clusters.
The estimated population being of 20.691 million, the interval
for determining the choice of clusters was of 118,237 (20.691
million/175).
Of these, according to the population, 11 clusters fell within the
3 missing provinces:
• 2 in Zabul Province;
• 3 in Paktika Province;
• 6 in Helmand Province.
In the remaining 30 provinces 164 clusters were selected.
Choice of Clusters for the Provinces
Where Population Estimates were
Available
• First the list in alphabetical descending order for
sampling (at province-level and at village-level) was
organised.
• The population for these clusters was of 20006246.
• The sampling interval was 20006246/164= 121989.3
• A random number gave the starting point, chosen
through the ALEA method 2 .
• The first village chosen was where the x th individual lived
• We thus proceed with the selection, always adding
121989 to the last selected number. Each village where
the chosen number individual lived was a selected
cluster for the NDSA.
Choice of Clusters for the Provinces
for Where Population Estimates were
not Available
We considered the provinces as stand-alone, or based on the
number of clusters already determined. This meant that each
province was considered as a separate entity and we selected
the number of clusters in each one according to our method. For
the population’s estimates, the projections that had been made
on the 1979 census data for these provinces were taken into
consideration and the cumulative population was calculated.
Then, for the provinces where we did not have the data, we
proceeded in the same manner as for the other provinces.
For the Province of Helmand
• The total population is at 756400;
• 6 clusters in this province have to be selected;
• The sampling interval is 126066.667 (756400/6);
• The random number selected through ALEA is Y 6 .
For the Province of Paktika
• The total population is 357300;
• 3 clusters in this province have to be selected;
• The sampling interval is 119100 (357300/3) ;
• The random number selected through ALEA is Z 6 .
For the Province of Zabul
• The total population is 249100;
• 2 clusters in this province have to be selected;
• The sampling interval is 124550 (249100/2);
• The random number selected through ALEA is W 6 .
At the end of this sampling frame, a list of 175 clusters was
selected according to population size and represented all the
provinces of the country.
2
For confidentiality reasons these numbers are not specified here
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<strong>Conducting</strong> <strong>Surveys</strong> on Disability: A Comprehensive Toolkit