II
John F. Altenburg United States Air Force Academy Lowell A. King and Carolyn Campbell Frank J. Seiler Research Laboratory USAF Academy, Colorado 80M0
Computer Grading of General Chemistry Laboratory Reports
1
en of the laboratory experiments in general chemistry are graded wholly or in part by a dieital comnuter. These ~~- exneriments are indicated in the table. We find in the' 750-student course t h a t grading time for each ex~erimentwhich is comdetelv computerized is reduced irom about 50 man-hours less than 10 minutes of total machine time. All laboratory report answers requiring calculations or calling for one of a fixed set of responses are computer graded. Essay or discussion questions and graphs are still hand-graded.
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Table 1.
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EXPERIMENT 6 CADET Sn CI cz il i 2 L o ........................................
...................... . . . . . . . . . . . . . . . . . . . . . . ... . . . . ............. ..............
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~ ~ , , , , , , . > , , 2 2 , 2 , , > , 2 , ~ 2 2 , , , 2 , , , 2 , , , , , , , , 1 1 , , , " , , , " , , " " , > , ~ , , , , , , , , , , , , , , , , , ~
4 1 . d 4 4 , , 4 . 4 1 a 4 4 4 a a a 4 a a 4 , a , 4 4 4 a a a 4 4 a , 4 4 , a :
. , , , . . , , , , , , , , , B . . , , , . , , , , , , , , . , , , , , , , , , ,
~ 1 1 1 1 1 , z z 8 1 1 1 1 1 1 1 , z z 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 , 1 1 1 1 , , , , , , , , , , ,
........................................
Figure
,,
A typical DATA card,
Experiments which are Computer Graded Svnthesia of a oomoler salt of iron1IIII determination of an empiricsl formula Percentage of water in a hydrate Reduotion of a metal oxide The molar volume of oxvaen An mid-base titration Tbermoehemistry: heats of reaotion Determination of ohlorids ion: Mohr titration Equivalent weight of a metal Oxidation-reduction titration
Our grading program differs from previously reported schemes for computer grading of examinations (1-6) in that sequential answers can be graded. That is, we are able to grade an answer for which one or more previous answers are required as input data. An error in one answer will not necessarily result in subsequent errors, if the calculations themselves are correctly performed. When an experiment is performed students record their data and observations on conventional laboratory report sheets. They also transcribe their data onto IBM PortrA-Punch cards (hereinafter called DATA cards) which are turned in to the instructor a t the end of the laboratory period.' A typical DATA card is shown in Figure 1. At the next class meeting each student turns in a completed laboratory report as well as a second PortA-Punch card (called the RESULTS card) on which his final answer and certain intermediate answers are given. A typical RESULTS card is shown in Figure 2. Since our laboratory sections are small (16 students), IBM PorbA-Punch cards contain 40 columns of perforated rectangles corresponding to the locations of the holes made by key punch machines. We use card No. D10688, with evennumbered columns perforated. A variety of cards, colors, and overprinting is available from IBM. We find that a sharp pencil is quite a satisfactory stylus for punching the data onto the cards. One of the experiments requires two DATA cards. Three values of the column 79 Rag are nsed, and a. similar correct seqoence test is made in this program.
Figure 2.
A typical RESULTS cord.
we have not found it necessary to identify individual students to the computer by social security numbers or other devices. Students' names are handwritten on the DATA and RESULTS cards, and the instructors arrange the cards for each of their sections in the order of the section roster. The only identification on the cards is the section number (columns 2 and 4), which' enables the computer to print the results for individual sections on separate pages. The pairs of student cards are assembled and machine processed. The cards first are checked by a program which examines for improper sequencing and illegal punches. DATA and RESULTS cards differ by flags in column 79, which have been machine punched before the cards are distributed to the students. If any two cards with the same value of the flag are read in sequence, one of the cards is out of order. A statement will appear on the printout sheet that a card is out of sequence, and the section number and the number of the card within that section will be printed.% If any column of any card is punched with a value other than a digit (a space is considered to be the digit zero), the card is reproduced on the printout page together with its section number and number within the section. About 0.2y0 of the cards contain such errors and it is a simple matter to resequence or repunch the offending cards, or return them to the instructors. Once all such errors have been corrected the grading begins. For each pair of cards the computer first Volume 45, Number 9, September 1968
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615
reads the DATA card and calculates what the final results should be. These answers are compared with the approved solution, and a technique grade is assigned for the student, which depends on the difference between the two. Columns are available on either the DATA or RESULTS card for the instructor to award a cut in technique grade if warranted by poor laboratory practice. The RESULTS card is read next, and the student's intermediate and final answers on the card compared with what he should have calculated. The student's first intermediate answer is compared with what he should have obtained from his data, had he performed all computations correctly. If they agree within preset limits (differences due to roundoff, slide rule precision, etc.) computational points are awarded. Next, the student's second intermediate answer is compared with what he should have correctly calculated from his reported first intermediate answer, whether or not the latter is itself correct. More computational points are awarded for a correctly performed calculation. This process is continued with successive intermediate answers (if there are any more) and the final answer. The course director establishes in advance each of the various technique and computational grades for the different answers in the laboratory report. The machine printout for each section provides for each student a repeat of his DATA card, three sets of results, and his technique, computational, and total grades. A portion of a printout page for one of the experiments is shown in Figure 3. The three sets of re-
Figure 3.
An excerpt from the printout page of one of the eiperirnenh.
sults are a repeat of his RESULTS card, the intermediate and final answers he should have obtained by correct calculation from each previous intermediate answer, and the intermediate and final answers he should have obtained from his original data if all calculations were performed correctly. Results for which no computational points were awarded are signaled by an asterisk following the student's reported value. Appropriate error messages are printed for students who submitted incomplete data or missing or incomplete results.
616
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Journal o f Chemical Education
WITH APPROVED SOLUTION. ASSIGN W ~ ~ A T I O UGRADE
Figure 4.
.%hematic representotion of the grading progrom.
Figure 4 is a schematic representation of the steps in the grading program. We provide more columns than are required on the RESULTS card so that the student must decide how many significant figures are required. We have been successful in grading for the correct number of significant figures in some experiments, and hope to extend this to all ten experiments. Cards are read, technique and computational grades assigned, printout pages composed, and course-wide statistics compiled by a series of sub-programs which are common to all of the experiments. The idea of computer grading has been generally popular with instructors and students. Hand-grading time and labor have been cut drastically, yet an .instructor still grades subjective questions, and may beas thorough as he wishes in his criticism of the student's calculakons on his laboratory report. Laboratory reports whose authors did not know how to go about properly treating the data are especially easy to spot, and the instructor has more time to give these papers the attention they deserve. Each student knows his paper will be checked ruthlessly for its accuracy, but fairly, and with exactly the same grading standards as apply to all of his classmates. Two of the common problems of hand-grading are less likely to arise: unwarranted good grades because of compensating student errors, and undeserved zeros because of incorrect student arithmetic. The grading programs were written in ALGOL and were run on the Rurroughs B-5500 of the Frank J. Seiler Research Laboratory (Office of Aerospace Research). Literature Cited (1) HINCKLEY, C. C., AND LAGOWSKI, J. J., J. CHEM.EDUC., 43, 575 (1966). (2) FRIOERIO, N. A., J. CHEM.EDUC.,44,413 (1967). (3) MANN,J. A,, JR., ZEITLIN,H., AND DELFINO, A. B.,J. CHEM. EDUC., 44, 673 (1967). (4) YANEY, N. D., J. CHEM. EDUC.,44, 677 (1967). (5) POLLNOW, G. F., J. CHEM.EDUC.,44, 679 (1967).
