COMPARISON OF METHODS TO DETECT ITEM PARAMETER DRIFT IN NABTEB SSCE FOR 2012-2015 CHEMISTRY MULTIPLE CHOICE TESTS USING IRT TECHNIQUES

Abstract

This study investigated the comparison of methods to detect Item Parameter Drift (IPD) in National Business and Technical Examination Board (NABTEB) Senior School Certificate Examinations (SSCE) for 2012 – 2015 Chemistry multiple choice tests. The main purpose was to examine the percentages of item drift and compare the differences in the number of drifted items across the stated examinations years using two IRT techniques (Robust –z and 3 -sigma IRT) of detecting IPD. This study was guided by three research questions and one hypothesis. The study adopted the Survey research design. The population of the study was 11,844 scores of candidates who sat for the National Business and Technical Examination Board, NABTEB, SSCE Chemistry multiple choice tests in Edo State, Nigeria. The sample size used for the study was 5,040 candidates’ scores. Multistage sampling technique was employed. The instruments used to generate data were 50 item National Business and Technical Examination Board, NABTEB, SSCE Chemistry multiple choice test items each for the four years (2012, 2013, 2014 and 2015) making a total of 200 items. The instruments being standardized by their source were considered valid and reliable. However, the item parameters were estimated from candidates’ responses using EIRT (Item Response Theory Assistant for Excel) software. The two methods (Robust- z method and 3 -sigma IRT method) were used to establish the IPD, descriptive statistics of frequency count and percentage were used to answer the research questions and the hypothesis was tested using Chi- square statistics at 0.05 alpha level. The results that were obtained from the analysis showed on the whole 20 items and 80 items drifted using Robust- z method and 3 -sigma IRT method respectively in 2012 – 2015 NABTEB SSCE Chemistry multiple choice tests and it was also found out that there is no significant difference in the number of drifted items in 2012 – 2015 NABTEB SSCE Chemistry multiple choice test items using Chi- square statistics. Furthermore, it was concluded that Robust -z method was the more stable method because it flagged the least number of drifted items between the two methods. Among others, it was recommended that NABTEB and other examination bodies should use Robust -z and 3 -sigma IRT methods to detect drift to avoid false identification of drifted items.