Number lines influence grade calculations, and grading scales influence perceptions and misconceptions.

Abstract

We examined U.S. college students’ ability to calculate hypothetical course grades as well as their perceptions and misconceptions about different grading scales (i.e., 100, 387, 400, and 1,000 total points). People often exhibit misconceptions, such as the whole number bias, when reasoning about rational numbers, such as fractions and decimals. One way to avoid these misconceptions is to support the visualization of magnitudes on number lines. In the current, preregistered experiment with 138 college-aged adults, the number line was beneficial for participants’ final grade calculations for the grading scale on which they were least accurate (387-point course). Aligned with instructors’ intuitions reported on the Society for the Teaching of Psychology’s Facebook page, participants endorsed grading scales that afforded the easiest conversions to percentages (i.e., 100- and 1,000-point courses); however, they reported a significantly stronger preference for the 1,000-point course compared to the 100-point course, even though no conversion to a percentage was necessary for this scale. Participants also reported being more willing to ask for grade boosts in the 100-point course compared to the other three courses. In addition to making some preliminary recommendations to educators, the current experiment provided initial empirical evidence suggesting that college students hold several misconceptions which affect their understanding of their course grades.