How accurate is peer grading?
Previously we showed that weekly, written, timed, and peer-graded practice exams help increase student performance on written exams and decrease failure rates in an introductory biology course. Here we analyze the accuracy of peer grading, based on a comparison of student scores to those assigned by a professional grader. When students graded practice exams by themselves, they were significantly easier graders than a professional; overall, students awarded ≈25% more points than the professional did. This difference represented ≈1.33 points on a 10-point exercise, or 0.27 points on each of the five 2-point questions posed. When students graded practice exams as a group of four, the same student-expert difference occurred. The student-professional gap was wider for questions that demanded higher-order versus lower-order cognitive skills. Thus, students not only have a harder time answering questions on the upper levels of Bloom's taxonomy, they have a harder time grading them. Our results suggest that peer grading may be accurate enough for low-risk assessments in introductory biology. Peer grading can help relieve the burden on instructional staff posed by grading written answers-making it possible to add practice opportunities that increase student performance on actual exams.
Department of Biology, University of Washington, Seattle, 98195, USA. srf991@u.washington.edu
Scott
S
Freeman
John W
JW
Parks
D001695:Biology / Q000193:education*; D003479:Curriculum; D004521:Educational Measurement / Q000379:methods*; D010379:Peer Group; D013334:Students