Assessing students' abilities to construct and interpret line graphs: Disparities between multiple‐choice and free‐response instruments

The author is concerned about the methodology and instrumentation used to assess both graphing abilities and the impact of microcomputer‐based laboratories (MBL) on students' graphing abilities for four reasons: (1) the ability to construct and interpret graphs is critical for developing key ideas in science; (2) science educators need to have valid information for making teaching decisions; (3) educators and researchers are heralding the arrival of MBL as a tool for developing graphing abilities; and (4) some of the research which supports using MBL appears to have significant validity problems. In this article, the author will describe the research which challenges the validity of using multiple‐choice instruments to assess graphing abilities. The evidence from this research will identify numerous disparities between the results of multiple‐choice and free‐response instruments. In the first study, 72 subjects in the seventh, ninth, and eleventh grades were administered individual clinical interviews to assess their ability to construct and interpret graphs. A wide variety of graphs and situations were assessed. In three instances during the interview, students drew a graph that would best represent a situation and then explained their drawings. The results of these clinical graphing interviews were very different from similar questions assessed through multiple‐choice formats in other research studies. In addition, insights into students' thinking about graphing reveal that some multiple‐choice graphing questions from prior research studies and standardized tests do not discriminate between right answers/right reasons, right answers/wrong reasons, and answers scored “wrong” but correct for valid reasons. These results indicate that in some instances multiple‐choice questions are not a valid measure of graphing abilities. In a second study, the researcher continued to pursue the questions raised about the validity of multiple‐choice tests to assess graphing, researching the following questions: What can be learned about subjects' graphing abilities when students draw their own graphs compared to assessing by means of a multiple‐choice instrument? Does the methodology used to assess graphing abilities: (1) affect the percentage of subjects who answer correctly; (2) alter the percentage of subjects affected by the “picture of the event” phenomenon? Instruments were constructed consisting of three graphing questions that asked students: (a) multiple‐choice‐choose a graph that best represents the situation; (b) free‐response‐draw a graph that best represents the situation. The sample of 1416 subjects from an urbadsuburban area in cluded 50% boys/50% girls from grades 8 through 12; subjects from high, medium, and low ability groups; and subjects from both public and private schools. The subjects completed either the multiple‐choice or the free draw instrument. The free draw instrument was scored by comparing the subject's response to categories of possible answers that had been identified from the first study. The results show as much as 19% difference in correct responses, three times as many “picture of the events” from multiple‐choice instruments, and significant differences in how multiple‐choice and free‐response affect various ability levels and grade levels. As such, some of the research studies that used multiple‐choice instruments to examine giaphing and the impact of MBL on student's graphing abilities may be invalid. © 1994 John Wiley & Sons. Inc.