P e e r I n s t r u c t i o n : A U s e r ' s M Peer Instruction: A User's Manual a n u Eric Mazur a l First Edition M a z u r F i r s t E d i t i o n ISBN 978-1-29203-970-1 9 781292 039701 Pearson New International Edition Peer Instruction: A User's Manual Eric Mazur First Edition International_PCL_TP.indd 1 7/29/13 11:23 AM ISBN 10: 1-292-03970-1 ISBN 13: 978-1-292-03970-1 Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.pearsoned.co.uk © Pearson Education Limited 2014 All rights reserved. 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ISBN 10: 1-292-03970-1 ISBN 10: 1-269-37450-8 ISBN 13: 978-1-292-03970-1 ISBN 13: 978-1-269-37450-7 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Printed in the United States of America Copyright_Pg_7_24.indd 1 7/29/13 11:28 AM 122123345670141719173171371 P E A R S O N C U S T O M L I B R AR Y Table of Contents 1. Introduction Eric Mazur 1 2. Peer Instruction Eric Mazur 7 3. Motivating the Students Eric Mazur 17 4. A Step-by-Step Guide to Preparing for a Peer Instruction Lecture Eric Mazur 23 5. Sample Lecture Eric Mazur 31 6. Epilogue Eric Mazur 37 7. Mechanics Baseline Test Eric Mazur 41 8. Force Concept Inventory Eric Mazur 53 9. Questionnaire Results Eric Mazur 67 10. Reading Quizzes Eric Mazur 71 11. ConcepTests Eric Mazur 101 12. Conceptual Exam Questions Eric Mazur 219 Index 241 I II INTRODUCTION The introductory physics course often is one of the biggest hurdles in the aca- demic career of a student.For a sizable number of students,the course leaves a permanent sense of frustration.I have only to tell people I am a physicist to hear grumblings about high school or college physics.This general sense of frustration with introductory physics is widespread among non-physics majors required to take physics courses.Even physics majors are frequently dissatisfied with their introductory courses,and a large fraction of students initially interested in physics end up majoring in a different field.Why does this happen,and can we do some- thing about it? Or should we just ignore this phenomenon and concentrate on teaching the successful student who is going on to a career in science? AN EYE OPENER Frustration with introductory physics courses has been commented on since the days of Maxwell and has recently been widely publicized by Sheila Tobias,who asked a number of graduate students in the humanities and social sciences to audit introductory science courses and describe their impressions.1The result of this survey is a book that paints a bleak picture of introductory science education. One may be tempted to brush off complaints by non-physics majors as coming from students who are a priorinot interested in physics.Most of these students, however,are not complaining about other required courses outside their major field.In science education,in Tobias’ words,the next generation of science work- ers is expected to rise like cream to the top,and the system is unapologetically competitive,selective,and intimidating,designed to winnow out all but the top tier. 1Sheila Tobias,They’re Not Dumb,They’re Different:Stalking the Second Tier,Tucson,AZ:Re- search Corporation,(1990). From Chapter 1 of Peer Instruction:A User's Manual, First Edition. Eric Mazur. Copyright © 1997 by Pearson Education,Inc.Published by Pearson Prentice Hall.All rights reserved. 1 Introduction The way physics is taught in the 1990s is not much different from the way it was taught—to a much smaller and more specialized audience—in the 1890s, and yet the audience has vastly changed.Physics has become a building block for many other fields,and enrollment in physics courses has grown enormous- ly,with the majority of students not majoring in physics.This shift in constituency has caused a significant change in student attitude toward the subject and made the teaching of introductory physics a considerable challenge.Although con- ventional methods of physics instruction have produced many successful sci- entists and engineers, far too many students are unmotivated by the conventional approach.What,then,is wrong with it? I have been teaching an introductory physics course for engineering and science majors at Harvard University since 1984.Until 1990,I taught a con- ventional course consisting of lectures enlivened by classroom demonstrations. I was generally satisfied with my teaching—my students did well on what I con- sidered difficult problems,and the evaluations I received from them were very positive.As far as I knew,there were not many problems in myclass. In 1990, however, I came across a series of articles by Halloun and Hestenes2 that really opened my eyes.As is well known,students enter their first physics course possessing strong beliefs and intuitions about common phys- ical phenomena.These notions are derived from personal experience and color students’ interpretations of material presented in the introductory course.Hal- loun and Hestenes show that instruction does little to change these “common- sense”beliefs. For example,after a couple of months of physics instruction,all students can recite Newton’s third law and most of them can apply it in numerical prob- lems.A little probing,however,quickly shows that many students do not un- derstand the law. Halloun and Hestenes provide many examples in which students are asked to compare the forces exerted by different objects on one an- other.When asked,for instance,to compare the forces in a collision between a heavy truck and a light car,many students firmly believe the heavy truck exerts a larger force.When reading this,my first reaction was “Not mystudents…!”In- trigued,I decided to test my own students’ conceptual understanding,as well as that of the physics majors at Harvard. The first warning came when I gave the Halloun and Hestenes test to my class and a student asked,“Professor Mazur,how should I answer these ques- tions? According to what you taught us,or by the way I think about these things?”Despite this warning,the results of the test came as a shock:The stu- dents fared hardly better on the Halloun and Hestenes test than on their midterm examination.Yet,the Halloun and Hestenes test is simple,whereas the material covered by the examination (rotational dynamics,moments of in- ertia) is of far greater difficulty or so I thought. 2Ibrahim Abou Halloun and David Hestenes,Am.J.Phys,53,(1985),1043;ibid.53,(1985),1056 ; ibid.55,(1987),455;David Hestenes,Am.J.Phys,55,(1987),440. 2 Introduction MEMORIZATION VERSUS UNDERSTANDING To understand these seemingly contradictory observations,I decided to pair,on subsequent examinations,simple qualitative questions with more difficult quan- titative problems on the same physical concept.An example of a set of such ques- tions on dc circuits is shown in Figure1.These questions were given as the first and last problem on a midterm examination in the spring of 1991 in a conven- tionally taught class (the other three problems on the examination,which were placed between these two,dealt with different subjects and are omitted here). 1. A series circuit consists of three identical light bulbs connected to a battery as shown here. When the switch S is closed, do the following increase, decrease, or stay the same? A B C S H (a) The intensities of bulbs A and B (b) The intensity of bulb C (c) The current drawn from the battery (d) The voltage drop across each bulb (e) The power dissipated in the circuit 5. For the circuit shown, calculate (a) the current in the 2-Ω resistor and (b) the potential difference between points P and Q. 12 V 4 Ω Q 2 Ω P H 6 Ω 8 V Figure1 Conceptual (top) and conventional question (bottom) on the subject of dc circuits. These questions were given on a written examination in 1991. 3 Introduction Notice that question 1 is purely conceptual and requires only a knowl- edge of the fundamentals of simple circuits.Question 5 probes the students’ ability to deal with the same concepts,now presented in the conventional nu- merical format.It requires setting up and solving two equations using Kirchhoff’s laws.Most physicists would consider question 1 easy and question 5 harder.As the result in Figure 2 indicates,however,students in a conventionally taught class would disagree. Analysis of the responses reveals the reason for the large peak at 2 for the conceptual question:Over 40% of the students believed that closing the switch doesn’t change the current through the battery but that the current splits into two at the top junction and rejoins at the bottom! In spite of this serious misconception,many still managed to correctly solve the mathematical problem. Figure3 shows the lack of correlation between scores on the conceptual and conventional problems of Figure 1.Although 52% of the scores lie on the broad diagonal band,indicating that these students achieved roughly equal scores on both questions (±3 points),39% of the students did substantially worse on the conceptual question.(Note that a number of students managed to score zero on the conceptual question and 10 on the conventional one!) Conversely,far fewer students (9%) did worse on the conventional question.This trend was confirmed on many similar pairs of problems during the remainder of the semester:Stu- dents tend to perform significantly better when solving standard textbook prob- lems than when solving conceptual problems covering the same subject. This simple example exposes a number of difficulties in science educa- tion.First,it is possible for students to do well on conventional problems by memorizing algorithms without understanding the underlying physics.Second, as a result of this,it is possible for a teacher,even an experienced one,to be completely misled into thinking that students have been taught effectively.Stu- dents are subject to the same misconception:They believe they have mastered the material and then are severely frustrated when they discover that their plug- and-chug recipe doesn’t work in a different problem. 80 80 Conceptual Conventional 60 problem 60 problem nt Average score 4.9 nt Average score 6.9 u 40 u 40 o o C C 20 20 0 H 0 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 Score Score Figure2 Test scores for the problems shown in Figure 1.For the conceptual problem,each part was worth a maximum of 2 points. 4 Introduction Figure3 Correlation between 10 conceptual and conventional prob- 1991 lem scores from Figure 2.The ra- 8 dius of each datapoint is a measure e of the number of students repre- r o sented by that point. c S 6 al u pt e 4 c n o C 2 H 0 0 2 4 6 8 10 Conventional Score Clearly, many students in my class were concentrating on learning “recipes,”or “problem-solving strategies”as they are called in textbooks,with- out considering the underlying concepts.Plug and chug! Many pieces of the puzzle suddenly fell into place: • The continuing requests by students that I do more and more prob- lems and less and less lecturing—isn’t this what one would expect if students are tested and graded on their problem-solving skills? • The inexplicable blunders I had seen from apparently bright students— problem-solving strategies work on some but surely not on all problems. • Students’ frustration with physics—how boring physics must be when it is reduced to a set of mechanical recipes that do not even work all the time! 5