Sampling Procedure
For the purpose of this study, multi-stage cluster sampling was used as no sampling frame containing all members in the universe or population exists. The sample was drawn in stages, with wards being selected at the first stage, dwelling
units within the wards being selected in the second stage and respondents selected at the third stage.
Phase 1
The wards formed the primary sampling units (PSUs). A random starting point(s) was used as a method to select the dwelling units to be surveyed. A total number of 602 wards in 4 provinces (Gauteng 448 wards), (Mpumalanga 72 wards), (North-West 70 wards) and (Free State 12 wards) were completed. A total of 6639 interviews were completed in these wards.
Phase 2
During the second phase, the field teams were required to complete a certain number of interviews, depending on the population size of that particular ward. The teams had to complete for an example in ward X 3 interviews and in ward Y they had to complete 33 interviews. This meant that the field teams had different target number of interviews that they needed to complete in all the pre-selected wards. Ward maps were obtained before fieldwork commenced, and random starting points were identified, marked and numbered on the map. This allowed for the random selection of one (if more than one existed) starting point. The field managers concerned will firstly identify where the starting point(s) is/are on the ground. Oncethat has been established he/she will from the starting point count 20 households from the starting point moving to his/her left. The 20th household that he/she has selected was the household were the interviews was supposed to take place Thereafter, the next 20th household was selected and approached until the target number of interviews was obtained.
The following process of household selection was adhered to: from the starting point 20 houses were counted in a ward. However, if there were:
• 1-5 target number of interviews to be completed in a ward; 01 starting point was used;
• 6-10 target number of interviews to be completed in a ward; 02 starting points were used;
• 11-15 target number of interviews to be completed in the ward; 03 starting points were used;
• 16-20 target number of interviews to be completed in the ward; 04 starting points were used;
• 21-25 target number of interviews to be completed in the ward; 05 starting points were used; and
• 25 and above target number of interviews to be completed in a ward; 06 starting points were used
In the case of a household refusal or if a selected respondent was mentally disabled, the household was immediately substituted with the household on the left. If still there was no interview completed then another substitution, going to the right of the originally selected household, was done. In case of non-contact whereby there was no-one home after two visits at two different times (afternoon and evenings) on the same day, the same substitution method was followed. Therefore, at least two-revisits at different times were done in cases where selected dwelling units, households or individuals were not at home i.e. non-contact. However, in some cases households visited after 19:00 on the day were substituted as agreed to in order to ensure that all the target number of households would be completed in the allocated time per ward.
Phase 3
For the purpose of this study, one randomly selected household respondent was selected per household. All household members qualified if they met the following criteria:
• Resident(s) of the household irrespective of nationality but excluding nonresidents and visitors; and
• 18 years of age or older
• In the event of a child headed household (all household members are under 18 years old), the oldest child was assumed to be the head of household, and should be interviewed
If more than one eligible person was found per dwelling unit, the ideal and most practical and accurate method of random selection of an individual was the use of a KISH grid. One individual per household was selected using the KISH grid after a comprehensive listing exercise was completed of all eligible individuals at the dwelling unit. Once the respondent had been selected the fieldworker will follow up only that person per household. If selected, substitutions could not be made where there were refusals or non-contact over a period of a day after two or more re-visits on the same day.
