Increase in student performance associated with LBLs. Student performance in 2009 (with LBLs) was significantly higher than 2007/8 (no LBLs) on four isomorphic and one identical (restriction enzymes) multiple-choice exam question pairs. Multiple Alleles and Restriction Enzyme question were Bloom's level 2, comprehension. Blood type, Ribosomes, and Nuclear Transport questions were Bloom's level 3, application. Percent correct represents the number of students who answered each question correctly of the total number of students who answered each question. *** p < 0.001, Fisher's exact test. The total number of students answering each question is indicated by numbers within each bar. These vary because there were two sections in 2008 and 2009, and not all questions were included on the final exams for each section. In addition, students who did not complete an LBL for a particular topic were not included in the analysis of the related LBL exam questions.