Table 3:
Expected sample size and precision under targeted child sample designs, by country: Population-based HIV Impact Assessment, 2015 -- 2017
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|---|---|---|---|---|---|---|---|---|
| Country |
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| Lesotho | Malawi | Namibia | Eswatini | Tanzania | Uganda | Zambia | Zimbabwe | |
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| Overall HIV prevalence for children age 0–14 (%) | 2.1% | 1.5% | 1.0% | 2.8% | 0.4% | 0.5% | 1.1% | 1.6% |
| Prevalence for children with HIV positive or deceased mothers (%) | 5.3% | 8.5% | 5.2% | 7.6% | 6.3% | 4.6% | 6.9% | 7.2% |
| Prevalence for children with unknown HIV status mothers (%) | 1.7% | 2.0% | 0.8% | 2.1% | 0.2% | 0.7% | 1.0% | 1.7% |
| Prevalence for children with HIV negative mothers (%) | 0.05% | 0.11% | 0.06% | 0.08% | 0.01% | 0.07% | 0.05% | 0.05% |
| Proportion of all rostered children with positive or deceased mothers | 26% | 12% | 13% | 27% | 7% | 7% | 12% | 15% |
| Proportion of all rostered children with unknown status mothers | 39% | 29% | 46% | 37% | 25% | 24% | 29% | 34% |
| Proportion of all rostered children with negative mothers | 35% | 59% | 41% | 36% | 69% | 69% | 60% | 50% |
| Neyman allocation sampling fractions (after accounting for non-response) | ||||||||
| Children with positive or deceased mothers | 90% | 78% | 95% | 92% | 97% | 95% | 85% | 88% |
| Children with unknown status mothers | 52% | 39% | 37% | 50% | 16% | 38% | 34% | 44% |
| Children with negative mothers | 9% | 9% | 10% | 10% | 4% | 12% | 7% | 7% |
| Expected number of children tested | 4,606 | 5,260 | 5,101 | 3,607 | 4,253 | 7,305 | 5,618 | 6,196 |
| Scenario 1: Neyman allocation design | ||||||||
| Expected design effect under optimal allocation | 0.69 | 0.64 | 0.63 | 0.71 | 0.35 | 0.54 | 0.50 | 0.61 |
| Expected RSE | 8% | 9% | 11% | 8% | 14% | 12% | 9% | 8% |
| Scenario 2: Modified Neyman allocation with sample reallocated from children with negative mothers | ||||||||
| Expected design effect | 0.60 | 0.57 | 0.52 | 0.62 | 0.25 | 0.58 | 0.40 | 0.51 |
| Expected bias in estimated prevalence | −0.02% | −0.06% | −0.02% | −0.03% | −0.01% | −0.05% | −0.03% | −0.02% |
| Expected RRMSE | 8% | 8% | 10% | 8% | 12% | 12% | 8% | 7% |
| Proportional reduction in MSE, compared to PHIA subsample design with equal sample size (Scenario 3) | 33% | 43% | 33% | 27% | 61% | 50% | 43% | 46% |
| Scenario 3: PHIA sub-sample design pro-rated to optimal allocation sample size | ||||||||
| Expected RSE | 12% | 14% | 15% | 11% | 31% | 24% | 14% | 13% |
| Actual PHIA results using the 50% household subsample design | ||||||||
| Number of children tested | 3,966 | 6,166 | 6,761 | 3,372 | 9,616 | 10,345 | 8,015 | 7,032 |
| RSE | 13% | 13% | 13% | 11% | 21% | 20% | 11% | 12% |