Item Difficulty and Discrimination Indices of Multiple Choice Biology Tests

This study empirically analyzed the item difficulty and discrimination indices of Senior School Certificate Examination (SSCE) multiple choice biology tests used by West African Examinations Council and National Examinations Council (NECO) in Nigeria. The researcher employed survey research design for the study. The sample for the study consisted of 1450 Senior Secondary Three students drawn from 20 randomly selected secondary schools. The instruments used for the study were 2008 the NECO and WAEC multiple choice Biology test papers. Item by item analysis was used for obtaining difficulty and discrimination indices. The classical test theory methods involving frequency count and percentages were used for obtaining the difficulty index and discrimination power.  Findings from the study showed that 2008 SSCE Biology multiple choice test had mean difficulty index of 0.42 and slightly higher than NECO Biology multiple choice test  with, mean difficulty index of 0.40 and 2008 SSCE in Biology had a discriminating power of 0.43 and higher than NECO with a mean discriminating power of 0.39. It was recommended that four option items in multiple-choice Biology tests should be encouraged but if five options items should be used more attention should be given to psychometric properties of tests.

 

Keywords: Difficulty Indices, Discrimination Indices, Multiple Choice Biology Tests.