Baseline Study of Striga Control using IR Maize in Western Kenya

1.2.2 Sampling strategyTwo factors guided the sampling strategy for this baseline study: the importance of maize andthe severity of Striga in maize production. Maize is grown in all the districts of the twoprovinces. Therefore, each district could be selected for this study. The rating of Strigainfestation can be quantified as follows on the basis of seed banks (Dr George Odhiambo,personal communication), low: 3 million seeds/ha. Using the above rating, experts contacted identified all the districtsor parts of districts in each province with high Striga infestation. Using an administrativemap of Kenya, four districts with high ratings of Striga infestation on maize were purposivelyselected in each province on the basis of their geographic closeness in order to minimize theresearch cost given the limited resources. The Ministry of Agriculture was then asked topurposively choose in each district one division and then one location with high Strigainfestation on maize. All the sub-locations in the chosen location were listed and two sublocationswere randomly selected; thus a total of 32 sub-locations for the two provinces. Theextension agents of the Ministry of Agriculture, known as front-line extension workers(FEWs) in Kenya, who had received a prior special training during a methodology workshopwere tasked to make the list of all the households within each sub-location from which theyselected 25 households randomly.1.2.3 Sample sizeEight districts out of a total of twelve districts were identified in Nyanza province. Thesedistricts had the highest Striga infestation. They were Bondo, Kisumu, Homabay, Migori,Siaya, Suba, Nyando and Rachuonyo. The four districts retained for this baseline survey andthe number of randomly selected households were Bondo, Kisumu, Siaya and Nyando. Ineach district 100 households were randomly selected. However, in Bondo district the FEWsmistakenly selected two additional households, thus a total of 402 households.Six districts out of a total of nine districts were selected in Western province. These districtshad the highest Striga infestation. They were Bungoma, Busia, Butere/Mumias, Kakamega,Teso and Vihiga. The retained districts for this baseline survey were Bungoma, Busia, Tesoand Vihiga. In each district 100 households were randomly selected, thus a total of 400households.The large sample size (802 households) was required as a result of the wide distribution ofStriga across several zones in western Kenya and as a result of the high population density inthe region. The selected villages and districts in the two provinces are shown in Figure 1.1.9