Table 1 Sampling stratification used to select schools in Oromia Regional State, Ethiopia, based on ecological zones defined according to epidemiologically significant differences in elevation and rainfall, based on classifications used by the Ministry of Health and WHO Ethiopia office [39]
Stratum description | Elevation (m asl)1 | Stratum | Total schools in stratum | Proportion of sample | Schools sampled |
|---|---|---|---|---|---|
Highland, occasional epidemic | 2,000-2,500 | 1 | 1651 | 0.1 | 20 |
Highland fringe, low unstable transmission | 1,750-2,000 | 2 | 1209 | 0.409 | 73 |
Highland fringe, high unstable transmission | 1,500-1,750 | 3 | 1163 | 0.393 | 71 |
Lowland with seasonal transmission (annual rainfall 500-1000 mm) | <1,500 | 4 | 389 | 0.132 | 24 |
Lowland with intense transmission (annual rainfall >1000 mm) | <1,500 | 5 | 196 | 0.066 | 12 |
Highland | >2,500 | 6 | 592 | Not included in survey | |
Arid lowland (annual rainfall <500 mm) | <1,500 | 7 | 4 | Not included in survey | |