The purpose of this study was to estimate the bias and design effects associated with the Expanded Program on Immunization's (EPI) sampling design when estimating xerophthalmia prevalence, and to estimate the savings associated with EPI in terms of distance travelled within selected clusters.
Computer simulation of the EPI sampling strategy was done using maps from a xerophthalmia survey of 40 wards in Sarlahi district, Nepal.
Samples of fixed cluster sizes of 7,10,15,20 and 25 were compared.
The estimated prevalence using the EPI design was compared with the true prevalence in the 40 wards to estimate the bias.
The design effect was estimated by taking the ratio of the variance under EPI sampling to that of stratified random sampling (SRS) with fixed cluster sizes.
The EPI was also modified by increasing the distance between selected houses from nearest neighbour to skipping 1-4 houses between selected ones.
The difference between the distance travelled within clusters using SRS compared with EPI was weighed against the bias and increased variance.
The prevalence of xerophthalmia was 2.8%. The EPI design overestimated xerophthalmia prevalence by between 0.27% and 1.16%. The design effects of EPI cluster sampling within wards varied between 0.73 and 1.35.
Neither the bias nor the design effect was related to distance between households or cluster size. (...)
Mots-clés Pascal : Xérophtalmie, Echantillonnage, Biais méthodologique, Epidémiologie, Méthodologie, Evaluation performance, Prévalence, Homme, Népal, Asie, Oeil pathologie, Conjonctive pathologie
Mots-clés Pascal anglais : Xerophthalmia, Sampling, Methodological bias, Epidemiology, Methodology, Performance evaluation, Prevalence, Human, Nepal, Asia, Eye disease, Conjunctiva disease
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 97-0534224
Code Inist : 002B30A01A1. Création : 13/02/1998.