The first stage of
sampling was the selection of countries. This selection
was stratified according to the WHO regions and the
levels of under-five child and adult mortality. Fourteen
sub-regions constituted the sampling frame for the first
stage of selection. From each sub-region, a total of four
countries were selected at random for participation in
the study, with probability proportional to the country
population. When the total number of countries was
less than four in any sub-region, all the countries were
included. This process resulted in 12 sub-regions having
four countries each and two sub-regions having three
countries each. A total of 54 countries were initially
pre-selected, but, due to operational and budgetary reasons, the WHO Global Survey project was implemented
in 24 countries from Africa, Asia and Latin America.
The second stage of sampling consisted of random
selection of two provinces/states (with probability also
proportional to the population size), in addition to the
capital city in these 24 countries. A third sampling stage
(also based on the population size but reaching sub-divisions below the province/state level) was used for ver