1. H. Berka,' P. A. C h r i ~ t i a n , ~ and M. W. Garaways Worcester Polytechnic Institute Worcester, Massachusetts 01609
Quantitative Analysis in General Chemistry
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Interactive programming to correct student cakulation errors
The application of computer technology to the teaching of chemistry lab courses has been limited mainly to performing complex calculations for students using their experimental data ( I ) and aiding the instructor in grading (2). Unfortunately, neither of these applications constitutes a learning experience for the students. Both Altenbure and coworkers (3a) and Johnson (36) have developed which indicate where errors have been made in student calculations, but no attempt is made to categorize specific errors. Also, the student is not given an opportunity to resubmit any corrected work. The input to Johnson's program consists of intermediate student calculated quantities which may he in error. Ayscough ( 4 ) has indicated plans to analyze student calculated results in order t o determine error-types to help instructors improve teaching, but no results are given. We have developed interactive computer programs which permit students t o check their calculations while they are still in the lahoratory. A student merely inputs his raw data and all calculated results for a particular experiment via a teletype terminal situated in or near the lab. This input is examined and the student is informed of any calculations in which he has erred. Furthermore, the nature of each error is specified by means of an appropriate error code. Repeated use of this program allows the student to correct his calculations while highlighting any conreptual hangups he might have.' This pmceis is analo. gous to "debugging" a computer program and artively ina student has calculated results volves the ...-students. Once consistent with his experimental data, then his laboratory techniques may he more meaningfully evaluated. Further details regarding our diagnostic procedures and computer programs and the complete results of our classification of student calculation errors into error-types as applied to two kinds of gravimetric determinations (precipitate collection and heating to constant weight) will be supplied on request.' Results obtained using interactive versions of our diagnostic programs are given in the table. ~
Summary of Results We have found that a considerable fraction of our technically oriented students in general chemistry turn in quantitative analytical results that are marred by calculation errors. These errors range in frequency from about 3% the averaee of two numbers. 13% in subtractin obtaining --ing two 6- or 7-digit numbers, to 52% in what appears to heasimole calculation involving the concept of a control (5). A signikcant fraction of the students omit the chemical factor in their calculation of % halide and % Ni. In fact, some students even omit their experimental data from their calculations. In a gravimetric determination involving duplicate samples we conclude that it is likely that at least 50% of the students will commit at least one calculation ermr in their treatment of the experimental data to obtain final results. In partial defense of our students, it has been pointed out to us by Prof. J. J. Zuckerman (Department of Chemistry, SUNY Albany) that one group of authors (6) found that about 10% of the calculated elemental percentage ~
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342 / Journal of Chemical Education
Percentaae of Students Having Error Free Calculations Experiment CIS
Nib
HsOb
Variable(8) Batch W t sample a n d wt AgCI: Funnel method 79 Filter paper method 42 %C1 (one calculation) 65 No errors throughout: Funnel method 52 Filter paper method 32 W t sample and wt NiO 63 %Ni (both calculations) 69 No errors throughout (includes mean %Ni) 48 W t sample and wt residue 50 %H.O (both calculations) 65 No errors throughout (includes mean 9oH10) 41
InteractiveC 96 98 100 96 98 98 100 97
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... ...
* Single determination.
Duplicate determinations. .At least one entry'was made a t a terminal by 106 students in the Ni-experiment and 105 students in the C1experiment. In the latter group, 47 used sintered porcelain funnels and 55 used filter paper (Ref. (5)) to collect their silver halide. compositions of organosilicon compounds in the literature are in error. The effectiveness of our interactive programs in helping students correct their calculation errors is strikingly illustrated by the comparison in the table with our previous hatch processed results. Most of the students using the interactive svstem were able to achieve final results free from calcuiation errors. Acknowledgment This work was supported in part by the DuPont Small Grants Program. The Worcester Area Colleges Computation Center (WACCC) provided generous donation of Presented, in part, at the 163rd National ACS Meeting, Boston, Massachusetts, April 13, 1972; at the Undergraduate Research Symposia, SUNY, Albany, New York, November 13, 1911 and December 2, 1972; at the Eastern Colleges Science Conference, USMA, West Point, New York, April 7, 1972. 'To whom all correspondence should be addressed at the Department of Chemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609. Present address: Department of Chemistry, Stanford University, Stanford, California 94305. Present address: 791 Parmenter Drive, Thousand Oaks, California 91360. 'Ideally, the instructor should examine the outputs received the first time students use the diagnostic program to identify the weak students who require personal attention as opposed to the rest of the students who do not. Students who make correct calculations or make trivial errors (e.g., in subtraction) gain little by having their calculations checked or rechecked by an instructor. Rather than replace the instructor, here the computer provides an efficient way for the instructor to have more time for real teaching of those studentswho need it mast.
computer time and facilities, we also thank the many WPI students who provided their data and evaluated this work. Literature Cited (11 (a) Cordus, A. A,, and Hsnmn, J. D., J. CHEM. EDUC., 12.485 (19651: (bl Jenscn, R. E.. Gamey, R. G., and Paulsoq B. A,. J. CHEM. EDUC.. 47, 147 (1970): lc) Wiberg. K.B.. J.CHEM.EDUC.47.113 l1970):smongothers.
(2) (a) Jon.& D. R.. and LNe. F. E., J. CHEM. EDUC.. 50,285 (1973): lbl h n d e m . R. E.. end Rush, Dl. H. A,, J. CHEM. EDUC.. 47, 139 11970): (c) Smith, S. R., khor. ~ . , ~ ~ d h ~ ~ h u~.CnEM~~~c.,1~,224(1965): e , ~ . c . , amongothers. (3) (a) Altcnburg, J. F., King, L. A,, and Campbell. C., J. CHEM. EDUC, 46, 615 (1968): lb) Johnson, R. C., J.CHEM.EDUC., 50,223l19731. (4) A ~ O U ~ ~ , P them . B . , i n ~ " t . 9.61 . 119731. (5) Gsddis, S. W., J.CHEM.EDUC., 38,5(19611. (61 BaLsnt. V.. Chvslwsky, V., and Rafhousk9, J.. "Orpsnarilieon Compounds,'' Val. L, (Tmnalolorr: Koiyk, A.. and SalBk, J.). Academic Press.NawYork, 1966, p.7.
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Volume 52, Number 5. May 1975 / 343
