The rationale for this study was to construct, administer and validate a mathematics achievement test for junior secondary school two students (JSS 2) in Oyo State, Nigeria. The instrumentation research design was used for the study. Purposive sampling technique was used in selecting two private schools in Ibadan metropolis; from which a total sample of 83 students in JSS 2 was purposefully and automatically selected as study sample. The test instrument was face-validated in terms of clarity of words and plausibility of distracter by specialist in the International center for Educational Evaluation, Institute of Education, University of Ibadan and experienced secondary school mathematics teachers. The MAT (mathematics achievement test) consisted of 200 multiple choice test items of four strata with Kudar-Richardson KR-20 reliability coefficient of 0.963 which was administered to 83 students and the response of these students were used in determining students’ mastery ability in the subject. The findings of the study show that the MAT is a valid and reliable instrument for measuring achievements in mathematics tests for junior secondary school 2 students; especially in Nigerian secondary school system. It is recommended that researchers, teachers and relevant educational stakeholders should constantly establish the reliability coefficient; difficulty and discrimination indices of test items they develop in measuring educational achievements so as to ensure the items are valid and relevant to the course objectives.
Keywords: Mathematics achievement test, Test, Testing, item analysis, item construction, standardisation.
