In a number of research studies involving surveys, the so-called Slovin's formula is used to determine the sample size. Unfortunately, many of these studies use the formula inappropriately, giving the wrong impression that it can be used in just about an

Year: 2012       Vol.: 61       No.: 1      

Authors: Lara Paul D. Abitona; Zita VJ Albacea

Abstract:

This paper aims to present methodologies in estimating the number of Vitamin A defi cient children aged six months to fi ve years in the Philippine provinces. Data from the 6th National Nutrition Survey (NNS), specifi cally, the data on plasma retinol which is used to directly determine Vitamin A defi ciency is used to compare direct and model-based methods. The direct estimates obtained was used as the dependent variable while the 2000 Census of Population and Housing and 2002 Field Health Service Information System were used as sources of auxiliary variables in the Poisson regression fi tted using robust standard errors which resulted to a model with Pseudo-R2 of 55.57%. Measures of precision and reliability were also obtained to assess the properties of the estimates for the provincial estimates. In direct estimation technique, 71 provinces have valid estimates but the coeffi cient of variations are all greater than 20%. On the other hand, valid model-based estimates using Poisson regression were observed for 72 provinces, but the coeffi cient of variations are at most 10% for 78% of these provinces. The use of Poisson regression based model generated more precise estimates of the number of children with Vitamin A defi ciency for the provinces.

Keywords: Small area estimation; Poisson regression model

Download this article: