CHAPTER 1.2: METHODOLOGY
1.2.3 SAMPLING .1 Household Survey
who do not have access to the mobile clinics or the hospital. The location of the hospital can be seen on the map provided in Appendix 1.2.1.There were eight primary schools and four secondary schools.
sample size to be able to test for significant differences in the prevalence of injectable use and/or experience of side effects between sub-samples of those surveyed. In consultation with a statistician and using the formula cited by Fleiss (1981,pAS)which includes the continuity correction, it was determined that 107 women should be selected in each injectable product user group (i.e. DMPA users and NET-EN users) to show a significant difference (at the 0.05level) in respect to the main side effects documented in the
literature (assuming at least 20% difference between the two groups) with 80% power. In this way it was predicted that approximately 200 injectable contraceptive users should be interviewed.The remaining women interviewed would either have discontinued use or never have used this method.The minimum sample size required, allowing for a 5%
sampling error and a 5% refusal rate, and using an estimated ratio of 3 non-users to one user of the injectable contraceptive (Abdool Karim, 1997),was determined to be 835 women. Thus it was determined that 40% of the estimated 2088 households should be visited.Further, in order to ensure an even spread of households across the sub-district, the sample was stratified by isigodi, selectively including a fixed sampling fraction in eachisigodi.A total of 848 women were interviewed.
Household Selection
A baseline mapping exercise of the Hlabisa sub-district had taken place prior to the survey. A starting point for the household interviews was selected in eachisigodi by blind random placement of a pencil mark on the isigodi map. Commencing from this selected point,the fieldworkers radiated out in different directions, each in a straight line.An interview was conducted at every second household until 40% of households in each isigodi had been visited. If no one was home or if a woman refused to be interviewed the
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nearest neighbouring household was visited.
Selection within a Household
Among women in the age range 15 to 49,one woman was randomly selected to be interviewed from each household visited.Only one woman was interviewed from each household to avoid within household correlation. The random selection was achieved by ascertaining the number of women resident in the household between the ages of 15 and 49. The age of each woman was recorded and a ribbon of a different colour was assigned to each woman of the household. One of these ribbons was then randomly selected and the woman to whom that coloured ribbon was assigned was interviewed.When arriving at the selected household, the interviewer was asked to comply with the following
procedure:
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Knock on the door.
Introduce yourself - show the letter of introduction.
Explain the study - give the person who answered the door the study information sheet.
Ask how many women between the ages of 15 and 49 live in the household.
Record the number and ages of the women living in the household on the sheet provided for this purpose. No names should be recorded.
If there is more than one woman,assign a different coloured ribbon to each woman, by entering the colour next to the age of the woman on the sheet referred to above. Select !m&.ofthese women in the following way:
if there is only one woman,she is the person who should be asked for her consent to be interviewed
if there are two or more women,draw one of the ribbons out of the box. The woman whose age corresponds with that ribbon colour should be interviewed
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if that woman is present,she is the person who should be asked for consent to be interviewed
if that selected woman is not in,ask when she is likely to be home. Ask if it would be in order to come back and talk to her at that time. Come back at the appointed time, introduce yourself, explain the study and ask for consent to interview her if she is not going to be back at any timeinthe next six days, re-select another ribbon and go through the selection process again amongst the remaining women of that household.
• If the person selected to be interviewed does not give consent, go to the house next door and go through the selection process again.
1.2.3.2 Focus Group Interviews
Community groups active in the study area were identified by key informants living in the area.At least one group of each type was selected for interview. Where two or more groups of the same type had been identified,a group was selected by convenience sampling, according to availability of the group and availability of a venue to hold a discussion. Focus group interviews were held with fourteen groups in all. The size and composition of each group and the characteristics of individuals within these groups are provided in Chapter 1.5, Table 1.5.3.
1.2.3.3 Analysis of Family Planning Clinic Records
An analysis of the records of contraceptive methods supplied by the family planning clinic of the Hlabisa Hospital was undertaken for the period July 1998 to July 1999.
1.2.4 COMMUNITY ENTRY AND ETHICAL SAFEGAURDS