Teaching lntroductory Chemistry: Generality of the PSI Approach Colin S. Davies Division of Learning Resources, Faculty of Education, Memorial University, St. John's, Newfoundland,Canada A1B 3x8 Since the introduction of the Personalized System of Instruction (PSI) to the educational fraternity a t large in 1968 (1), many reports (2-26) have appeared describing its application to chemistry teaching. Ranging from the qualitative to the quantitative, these reports indicate the extent to which the PSI approach has been used for teaching chemistry. For example, varying degrees of success have been achieved with many variations of the basic PSI model; with students enrolled in a variety of degree programs a t hoth universities and colleges; for courses ranging from general chemistry, to organic chemistry, to quantum mechanics; and for courses with enrollments ranging from less than 20 to more than 200. From these reports, it would seem that PSI is at least as good as, and possibly better than, the lecture-discussion approach for teaching chemistry; furthermore, many students and instructors have been positive in their evaluation of the PSI approach. However, for all chemistry teachers and especially for those who may be contemplating using the PSI approach, several important questions remain unanswered. There appears to have been little or no attempt in PSI chemistry courses to examine the effects and utility of instructor-pacing, i.e., where deadlines for the completion of certain requirements (e.g., a unit quiz or review exam) are set by the instructor to influence the rate a t which students may progress through the course. Although required to complete courses within one semester, students have for the most part found themselves in the novel situation of self-pacing, i.e., having been able to determine their own rate of unit completion for the whole semester (4, 6, 7, 9-13, 16, 17, 19-21, 24, 25). Even though the use of deadlines has been reported (2,261, only one deadline was used in each case, occurring approximately three to four weeks into each course. Requiring tests to he taken on specified dates only appears to have been tried in one study (8). In most courses (2-4, 6, 7, 9-12, 14, 17, 19, 22-26), too, grades have been based on combinations of hoth the number of units completed and examination performance; that is, students have received direct credit toward course grades for completing each unit. The experience of inplementing PSI courses in which course grades are based on examination scores alone has received little at,tention (5); in such courses, students receive only token credit for completing each unit, each unit completed constituting a body of learned material and permitting progress to the next unit. Finally, the relative effectiveness of PSI and lecture-discussion approaches for teaching chemistry remains in doubt. Superiority similar to that found for PSI in psychology, statistics, engineering, and biology (27) has not been demon-
686
Journal of Chemical Education
strated clearly in chemistry where reliable conclusions have been limited by methadolc&al problems. Such restrictions have been inherent in comparisons of PSI and lecture-discussion groups on the basis i f course grades (4,15,18,23),the assessments of which may not necessarily have shared the same criteria. Althoueh " examinations common to bath PSI and lecture-discussion groups represent a more reliable basis, com~arisonsbased on exams (4.9.16.18.23.241 . . . , , , , and course grades have suffered from hoth the uncertain equivalence of the rrouus heine com~areddue to the need to work with intact rathkr than ran&mli selected groups, and the differential loss of students. This threat to validitv has been even ereater ~~~~~
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the basis of hoth examination scores (5, 8 , 1 2 , 16, 22) and course grades ( 2 , 3 , 6 , 8 , 2 6 ) .Pasternack (19) addressed this problem by selecting PSI and lecture-discussion groups a t random; however, interpretation of the results is complicated by the fact that not all students wrote the same exam, and scores were adjusted to account for differences in difficulty of the exams. In reporting the experience of using PSI for teaching introductory chemistry courses a t Memorial University, this study addresses these issues. Without compromising any essential components, the PSI approach was implemented in as much of the traditional lecture-discussion setting as possible; course assessment was hased on review exams and a final exam, all of which had to he written a t scheduled times. Using analysis of covariance, a reliable demonstration of the relative effectiveness of PSI and lecture-discussion approaches for students differing in academic background was achieved. Introductory Chemistry Courses Memorial University of Newfoundland offers a sequence of two one-semester credit courses in introductory chemistry, Chemistrv 1000. and Chemistrv 1001. The first of these courses, chemistry 1000, is available to students with a strong chemistry background (such as provided by successful completion of the two-year high school Chem Study program) in the fall semester as shown in Figure 1: as indicated bv the broken line, though, students wh:) have not taken chemistry in high school are also permitted to enroll in Chemistry 1000 provided a high level of academic achievement has been demonstrated in other subjects, especially mathematics. Students must attain a t least a passing grade in Chemistry 1000 before being allowed to euroll in Chemistry 1001. Chemistry 1000 includes such topics as the mole concept and stoichiometry, energetics, atomic structure and periodicity,
chemical bonding, molecular geometry, structure and hehavior; Chemistry 1001 includes reaction kinetics, equilibria, oxidation-reduction, electrochemistry, and an introduction to organic chemistry. Students who do not meet the criteria for entry into Chemistry 1000 are required to enroll in a one-semester non-credit course, Chemistry 100F. The course is designed to prepare students with a weak chemistry background for the Chemistrv 1000/1001 sequence offered in the winter and spring semesters, respectively, as indicated in Figure 1. Chemistrv lO0F includes simvle atomic structure and periodicity, mole concept and stokhiometry, nomenclature, formulas and equations, gas laws, and solutions. Chemistry 1000H001-PSI: Course Design
The content of each one-semester course was divided into 15 units. For each unit, students were orovided with a stud? guide which consisted of the following: a brief introduction, to serve as an advance organizer for a unit's content as well as providing a link with the preceding unit(s); a list of objectiues, specifications of what a student should know and he able to do having completed a unit; a list of study activities for either one objective or a group of closely related objectives (such activities were designed to keep the student actively responding and included, for example, reading passages in the required texts (28, 29), plotting graphs, analyzing data, viewing films); a set of study questions, hased on hoth individual ohiectives and combinations of ohiectives.. to ureuare . . students for the types of questions to be expected on review and final examinations as well as anizzes for each unit: and answers to study questions, which varied from page references to where answers could he found in the texts to step-wise listings of model answers for problems and calculations. Additional information or announcements were provided on printed handouts. No lectures were given -during the course. Students were required to work through the units in turn, and when ready they were required to write a quiz on each unit. If a score of 90% (or better) was ohtained, the student was handed the study guide for the next unit; if a score of less than 90% was ohtained, students were required to write another quiz on the same unit. Advancing to the next unit was allowed onlv if the 90% uerformance criterion was attained on a unit. even if a number of quizzes had to he taken. For most units, three alternate quiz forms were available although as many as five forms were prepared for some units. Unit quizzes consisted solely for which students were exvected - of auestions . to construct and write their own answers. On average, the quizzes took from 20-30 min to complete. T o encourage serious study habits and to prevent frivolous quiz taking, students were required to wait 30 min after not achieving the 90% passing criterion on a unit quiz before taking another quiz on the same unit. Students did not receive credit toward their course grade for the successful completion of each unit. Upon completion, students brought their unit quizzes to proctors for grading. Proctors were students who had previously completed hoth Chemistry 1000 and 1001 with an A grade (80%.or better). Each vroctor was scheduled for three of the six class hours per week to maintain a proctor:student ratio of about 1:lO. Since it was not possible to offer course credit for their services, student proctors were paid a t the same rate as student demonstrators in undergraduate lahoratorv . classes. A period of one semester was allowed for the completion of each course, and it was announced that incompletes would he hard to get. Withdrawing from a course a t Memorial is required within the first two weeks of the semester to avoid any financial penalty and within the first eight weeks to avoid any academic penalty, i.e., recording of course enrollment and subsequent withdrawal on transcript. Although student progress was controlled within the semester period by the scheduling of three review exams, each covering five units,
aouroximatelv four weeks were availahle for student self.. pacing prior to each review exam. Two different dates were scheduled for the completion of each review exam and the final exam; the earlier dates allowed course completion two weeks before the end of the semester whereas the later dates were arranged so that the final exam would he written during the regularly scheduled examination period a t the end of the semester. students were expected to have completed all necessary units prior to each review exam. However, students who failed to do this were given the units they had not completed and then required to write the exam on the later date. Units that were handed out in this way had to he completed before any subsequent units could he ohtained. Finally, an oroeress additional influence on student . - was reauired weeklv attendance a t a laboratory session, the content of which was often correlated with course units that should have been completed previously. Course grades were based in part on the three review exams . and final exam, respectively comprising 30% and 60% of the overall assessment: the remaining 10%of the assessment was based on performance in the ten.weekly 3-hr laboratory sessions. Review exams and the final exam were graded by the instructor. Comparison of PSI and Lecture-Discussion Approaches
In order to determine the relative effectiveness of the PSI andlecture-discussion auoroaches for teaching" introductorv .. chemistry, student performance under the two approaches was comvared in three sevarate studies. As far as uossihle. hoth P S and ~ lecture-discussion groups were treated in the same way so that they should differ only in terms of the instructional approach. Students in lecture-discussion groups, for example, met for approximately the same number of hours each week, used the same text and course objectives, and wrote the same final exam a t the same time as students in the PSI group. Under the lecture-discussion approach, however, class time was devoted to the presentation of essential course content, class discussion, and tutoring. Student attendance was expected a t each class meeting. Students were not required to demonstrate any competence on each unit before advancing to the next and, hence, did not write a quiz on each unit. Study 1: Chemistry 1000-PSI (Fall Semester)
Of the 23 students that volunteered for Chemistry 1000PSI, the first introductory chemistry course to he offered a t Memorial using the PSI approach, 21 (91.3%) obtained passing grades and 2 withdrew. Student pnrgress in the course was followed by determining the average unit comuleted bv the rrouu. as a whole on any given course day; this index, the mean unit completed, was calculated in the following way: Mean unit completed =
Total number of units completed Number of students
An indication of the mean rate of unit completion by the group was ohtained hy plotting this index against course day, as shown in Figure 2. In general, the rate of unit completion was
Figure 1. Enrollment criteria and sequences of introductory chemistry courses.
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Number 8
August 1981
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Course Doy Figure 2. mester).
Mean
rate
of unit
compietion in Chemistry 1000-PSI (Fail Se-
Figure 3. mester).
rate of unit compietion in Chemistry 1001-PSI (Winter Se-
Table 1. Mean Percent Exam Scores of Students in Chemistry 1000 (Fall Semester)
well sustained throughout the semester, heinr frequently at, and even above, the projected uniform rate. The deceleration in rate around coune day 20 accompanied the bepinninp of attempts on three of the more demanding units of the course, Units 6, 7, and 8, Ionization Energies, Periodic Tahle and Chemical Reactions, and Mole Concept, respectively; the acceleration beginning around course day 35 accompanied student progress on some of the more qualitative and less quantitative units (e.g., Atomic Structure, Chemical Bonding, and Molecular Geometrvi and the onset of the last three weeks d t h e ,rurie. 'I;,rhc rr;e,~rrh.~tthe meart unir in the course, n o t all students completed all 15 units. Tahle 1 summarizes the mean percent review and final exam scores of students in the PSI group and a Chemistry 1000 lecture-discussion group (n = 22) taught by the same instructor. Without exception, the average performance of PSI students was hetter by 7.7-12.4%.
Table 2.
Study 2: Chemistry 1001-PSI (Winter Semester) Forty-two students volunteered for Chemistry 1001-PSI, of whom 37 (88.1%)ohtained passing grades and 5 withdrew. The mean rate of unit comoletion. as illustrated in Fieure 3.
5CDreS
previous semester, not all students completed all the units. Since the instructor responsible for the PSI group did not also teach a lecture-discussion group of Chemistry 1001, the performance of PSI students was compared to that of lecture-discussion students taught by other instructors; a final examination common to all students formed the basis for the I t~mpurimm. I l ~ ~ a . r \ ~itewr ,i s nut p
