R. D. Rosensteinl and 5. R. Smith
Using Computing Machines to Grade
University of Connecticut Storrs
Student Analysis Reports
The increasing availahility of high speed digital computers and the relative simplicity of Fortran programing makes the use of machine methods a useful aid in the grading of laboratory reports in a course of quantitative analysis. We have prepared a grading program for an IBM 1620 on the following basis. Each student carries out the analysis of his unlmown in triplicate and reports these results. A perfect analysis is worth 100 points. The grade is based on the parts per thousand error (C) of each of the three determinations. The student is allowed an error (precision factor) of F parts per thousand on each of his three determinations without a deduction; however, if the error exceeds this, a deduction of C/F points for each part per thousand is taken, up to a maximum of E points per determination. Thus the lowest grade for reporting three determinations is 100-3E points, given for carrying out and reporting the experiment. An arbitrary deduction Q is taken for omitting one determination; for two omissions, P Q points are deducted. The Fortran source program for this grading scheme is available in our library. In practice the student will he issued an IMB card punched with his name (about 15 can be prepared for
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' Present address:
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University of Pittsburgh.
Journal of Chemical Education
each student each semester) on which he will write the results of his experiment. These results will be punched on the card by the laboratory assistant or computer technician. The correct analysis for each group of identical samples and the basis for deductions will be punched on a control card, along with the title of the experiment. To begin the calculation the control card is read into the machine and the title of the experiment is recorded; this is followed by the first student's data card. The program has been set up to perform the following operations: 1. The error ( C ) of three experimental determinations in parts per thoussnd from the correct value (S). 2. Deduct C / F points for each pmt per thousand up to a maximum of E points per determination regardless of the magnitude of the error. (However, if the student's error falls within F parts per thousand no deduction is made.) 3. Deduct a suitable penalty in the case of f d u r e to report d three required determinations. The penalty for failing to report one determination is Q points, the penalty for failing to report two determinations in P Q points. 4. The student's mark M. 5. The average of the values reported by d l ~tndentefor the same unknown and the average mark for thirr group. 6. The number of students who analyze the same unknown.
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After the calculation the machine punches and types the following information: the student's name, his
reported values, the correct value, the maximum number of points deducted for each determination, the precision factor, and the mark. Following the printing the next student's card is entered, calculated, and recorded as above. The series is terminated with a blank card. The correct value, maximum deduction, and precision factor are reproduced with each analysis so that the student may have a record of this information when his card is returned to him. Refore the next control card is read into the machine, the number of students, the average grade and the average analysis for this series is tabulated for the instructor's information. Consider the experiment where the correct percentage composition (8)of chloride in a sample is 50.00. The maximum number of points (E) that will be deducted per determination is 20. The precision factor (F)is 2.0. The number of points (Q) deducted for failing to report one determination is 10.0. The number of points (P) deducted for omitting a second determination is 5.0. A control card is prepared as follows CHEM 232 CHLORIDE ANALYSIS 20. 50.00 2.0 5. 10.
Nine students have analyzed this sample. Their punched cards contain the following input data for the machine, as shown in Table 1. The results of the calculations are shown in Table 2. Table 1.
Student Data Reported for Chloride Analysis"
Fekete Finnerty Kent Kuehl Munnelly Paton Rosenstein Roure Smith a
Paton who has reported only one analysis whose error is 70.4 ppt, is marked as follows 100.0 - 20.0 - 5.0 - 10.0 = 65
He has gained by reporting honestly rather than manufacturing two additional results similar to the one he. obtained. The complete report tabulated for the instructor is shown in Table 2. The last line indicates the number of students reporting (9); the average grade (75), and the average analysis (51.12). A series of sets of determinations can be calculated in sequence. The time required for processing the data shown in Table 2 is Z1/2 minutes. The authors realize that different instructors may employ other systems of grading, for example a system of non-linear deductions, or a system that grades separately on the basis of accuracy and precision. These could be incorporated into a program similar to the one reported here. The program is based on a method that has been successfully used without machine calculation, and we wish to demonstrate that machine calculation can save time and increase accuracy. An extension of this work would involve checking the student's calculations before assigning a grade. This would require reading all the students experimental data into the computer and then using a program specific for the experiment that is being marked; the machine calculation would be compared to the one reported by the student, and the final grade adjusted for the student's arithmetical errors Table 2.
Tabulated Results of Student Analysis
~ C h e 232 m Chloride Analysi-(1)" (2) (3) (4) (5)
The correct analysis should be 50%.
To illustrate the computation, Smith's errors C,, CZ, Caare 5.0, 7.6, and 0.0 ppt for the three determinations. This leads to the following mark rounded up to the nearest integer:
For Rosenstein, the grade is computed as follows: C, and Cz are each below the precision factor 2.0 so no deduction is made. Ca is above the maximum deduction 20 so that the mark is computed as follows: 100.0
- 0.0 - 0.0 - 20.0 = 80
(6)
(7)
Fekete Finnerty Kent Kuehl Munnelly Paton Rosenstein Ronre Smith *Columns (11, (21, and (3); student data (%I1 (4) correct analysis; (5) maximum deduct~ons per determmatmn; (6) precismn factor; (7) final grade. Data of nine students show an average grade of 75; average analysis, 51.12.
We wish to thank Professor J. L. C. Lof, Director of University Computing Center, and members of his staff, for their cooperation during this work; and we wish to thank the National Science Foundation for support of the computing facilities a t this University.
Profiles of NSF Institute Participants Dr. Chmleles L. Koelsch, Professor of Science Education at the University of Georgia, Athens, has prepared two extensive sunrep, "Characteristicsof Persons Submitting Applications in 1962 for Participation in NSF Programs at the University of Georgia!' One covers junior highandelementary school personnel; the other, secondary school science teachers. These studios will be of interest to those wanting to sample the facts about teachers interested in self-improvement. Copies are available on request to the author. Volume 39, Number 12, December 1962
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