Table 1 Sampling and sample size for quantitative and qualitative methods
Groups | Sampling method | Sample size | Assumptions |
|---|---|---|---|
Quantitative phase sampling and sample size | |||
Survey of health centers | Sampling health center survey: A stratified simple random sampling method was applied for the selection of health centers. Health centers were stratified by sub-city. Lottery method was applied to select 5 health centers from each of the 10 sub-cities | The sample size for the health centers survey (maternity unit heads interview, register review, and observation) Health centers were stratified by the 10 sub-cities. Simple random sampling – a lottery method was used to select 5 health centers from each of the 10 sub-cities in Addis Ababa city | Half of the population was included in the study. A sample > 30 is sufficient to do a parametric test (Rule of thumb) |
Survey of women in the post-partum period [9] | Sampling women survey: 10 women were interviewed from each of the 50 health centers Systematic random sampling was used to select 10 women who were 6 h to 6 weeks in the post-partum period. Women were selected from all eligible women who were in immediate post-partum care or who came to the health center for post-natal care during the 2 days visit to each of the health centers [9] | The sample size for women interview [9] \({n}_{1}={n}_{2}=\frac{{\left({z}_{a/2}\sqrt{2\overline{pq} }+{z}_{\beta }\sqrt{{p}_{1}{q}_{1}+{p}_{2}{q}_{2}}\right)}^{2}}{{\Delta }^{2}}\) \(\mathrm{Calculate} \overline{p }=\frac{{p}_{1}+{p}_{2}}{2}.\) = 0.25 + 0.15 = 0.2 2 ∆ = p1-p2 = 0.25—0.15 = 0.1 n1 = n2 = (1.96 √.2*.8 + 0.84 √0.25*0.75 + 0.15*0.85)2 (0.1)2 n1 = 250 n2 = 250 n = n1 + n2 = 500 A study in Addis Ababa reported client satisfaction of 20% on intrapartum care [10] | P1 = % client satisfied with the care at facilities with high-quality score = 25% P2 = % client satisfied with the care at facilities with low-quality score = 15% 95% Confidence interval (Z ∝ /2 = 1.96) Power 80% (Zβ = 0.84) |
Survey of midwives | Sampling midwives’ survey: All midwives working in the 50 health centers and available during the study period were interviewed using a structured questionnaire | The sample size for midwives’ interview n = (Z∝/2)2 pq d2 n = (1.96) 2 0.53 (0.47) = 390 (0.05) 2 P = 0.53 q = 1-p = 0.47 d = 0.05 Correction for finite population nf = n/(1 + n/N) + 15% (n) addition for non-response nf = 390/(1 + 390/1200 + 15% (390) = 339 The sample size required after correction for a finite population was 339 midwives A study in Addis Ababa reported job satisfaction among midwives of 53% [11] | The proportion of midwives who were satisfied in their job = 53% The margin of error (d) = 0.05 95% Confidence interval (Z ∝ /2 = 1.96) N = 1200 number of all midwives in Addis Ababa |