A diagnostic assessment for introductory molecular and cell biology

Abstract

We have developed and validated a tool for assessing understanding of a selection of fundamental concepts and basic knowledge in undergraduate introductory molecular and cell biology, focusing on areas in which students often have misconceptions. This multiple-choice Introductory Molecular and Cell Biology Assessment (IMCA) instrument is designed for use as a pre- and posttest to measure student learning gains. To develop the assessment, we first worked with faculty to create a set of learning goals that targeted important concepts in the field and seemed likely to be emphasized by most instructors teaching these subjects. We interviewed students using open-ended questions to identify commonly held misconceptions, formulated multiple-choice questions that included these ideas as distracters, and reinterviewed students to establish validity of the instrument. The assessment was then evaluated by 25 biology experts and modified based on their suggestions. The complete revised assessment was administered to more than 1300 students at three institutions. Analysis of statistical parameters including item difficulty, item discrimination, and reliability provides evidence that the IMCA is a valid and reliable instrument with several potential uses in gauging student learning of key concepts in molecular and cell biology.

Figure 1.

Item difficulty (P) values for each question on the IMCA for Fall 2008 and Fall 2009 pre- and posttests. P values represent percentages of correct answers. Results are based on the 671 students who took the pre- and posttests in class. Yellow bars show the correct answer percentages for each question on the pretest; green bars show the increases in correct answer percentages between pre- and posttest for each question. Questions are grouped according to learning goal (see Table 2).

Figure 2.

Item discrimination (D) values for questions on the IMCA for the 671 students who took the pre- and posttests in class. Questions with substantial increases in P value (Figure 1) and low D values on the posttest (most students answered correctly) correspond to concepts on which most students gained understanding during the course. Questions with high D values on both the pre- and posttests correspond to concepts that primarily only the stronger students understood at both the beginning and end of the course (see Discussion for further explanation). Questions are grouped according to learning goal (see Table 2).