This study identified biased test items in the Rivers state JSSCE Business Studies conducted in 2009 using Item Response Theory Approach. The Sample comprises 4000 JSS III students in public and private schools that sat for the JSSCE Business Studies Examination in 2009 in Rivers state which were selected through stratified proportionate random sampling. The instruments for data collection were the test items in JSSCE Business Studies conducted in 2009 and a result collection sheet. Two null hypotheses drawn from two research questions were tested at 0.50 probability of correct response. The assumptions of unidimensionality and local independence were checked using factor analysis. The students’ responses to the test items were calibrated with an IRT statistical software named ex-calibre 4.2.2 developed by Assessment Systems Corporation. The results revealed that the test items met the assumptions of unidimensionality and local independence. It also revealed that there is school type bias in the Rivers State JSSCE Business Studies test items for 2009. Based on the findings, recommendations were made, one of them being that business studies curriculum should be restructured so as to accommodate the new technological advances which may be one of the reasons for the presence of school type bias in the Business Studies test conducted in 2009 in Rivers State.
Keywords: Item Characteristic Curve, Item Response Theory, Unidimensionality
