Assessing the dimensionality and local independence of WASSCE 2018 Mathematics objective tests scores in Lagos State, Nigeria

Abstract

This research work is a descriptive survey design type aimed at investigating the extent to which the 2018 African Senior Secondary Certificate Examination Mathematics objective tests items fulfil the unidimensional and local independence assumptions. All the year three Senior Secondary School students (SS3) of the I ,647 senior secondary schools that registered for the 2020 WASSCE in Lagos State formed the population for the study. The sample for this investigation comprised 1334 (SS3) students from 18 schools which were randomly selected from the six educational districts of Lagos State (three schools from each educational district). Two research questions were raised and analyzed using Stouts test of essential Unidimensionality, conducted in DIMTEST version I .2.0 and hén Q3 statistics. Findings indicated that the 2018 WASSCE (SC) Mathematics objective items did not meet the assumption of Unidimensionality and that there is more than one dimension that accounted for the variation observed in examinees' responses to the mathematics test items. In addition, some items violated the assumption of local independence because their correlation residuals are greater than >0.2. Hence, test developers and the external examining bodies are encouraged to be open to the use of IRT and standard statistical methods for estimating test parameters to ensure the quality of the assessment instrument.