A METHOD OF AVERAGING GRADES IN LABORATORY COURSES
-
The final grade in a laboratory course is fixed ordinarily by the consideration of a t least three distinct numerical grades for each student, namely, laboratory work, class work, and the final examination. The weights to be assigned t o each of these units will vary with the nature of the particular course. Unless the averages of the class for each of these units are a t least approximately the same, even the weighted grades derived from these will not give a correct estimate of the relative abilities of the students in the class. Take, for example, a class in qualitative analysis in which the final laboratory-work grades range from 75 t o 98, with a class average of 90, and in which the class-work grades range from 40 to 90 with an average of 60. An average student, A, receives a grade of 90 for laboratory work and 60 for class work. The resultant of these is 75. Student B receives 95 for laboratory work and 55 for class work. The resultant here is likewise 75. From a consideration of the wide numerical range of the class-work grades and the limited range of the laboratory grades for the entire class, it should be evident that the diierence of five points in laboratory work ought to be of more significance than five points in class work. I n the cases cited above, student B should, therefore, receive a higher grade than student A, whereas by the ordinary process of calculation, the two grades work out to be identical. To eliminate this situation, the author has used the following scheme for four years with considerable satisfaction. The class-work averages for the members of the class are made out in the usual manner. These are then arranged in numerical order, the highest grade standing a t the top of the list. The student receiving the highest grade is given the number one, the second highest the number two, etc. In the case of a tie, identical numbers are given. Thus, if the grades in a class run 90, 88, 88, 85,-, the numbers assigned would be 1, 2. 2, 4, --, respectively. The same procedure is employed in determining the corresponding number for the laboratory-work grade. When these numbers for each student are added together, a number is obtained which may be designated as the ranking number for the student. A comparison of the ranking numbers of the members of the class gives a relative measure of the rank of these, the better ones having the smaller ranking numbers. Suppose the students A and B, cited above, are in a class of twenty. Student A would receive number 10 for class work and 10 for laboratory work, or a ranking nnmber of 20. Student B would receive perhaps 12 for class work and 4 for laboratory work, or a ranking number of 16.
This would give student B a higher ranking than student A, whichis what he really deserves. This method may readily be extended to include the examination and other grades. Suppose the total grade is to consist of class work (two units), laboratory work (two units), and final examination (one unit). In such a case the numbers obtained for the laboratory grade and for the class grade would each be multiplied by two and added to the number obtained for the final examination to give the ranking grade. These may then be placed in numerical order, and letter grades assigned to each student. There is no reason why the ranking numbers should not be converted into (relative) numerical grades on any scale desired. Any weighti n g ~may be given to the various units, and additional units may be added to meet the requirements of any class, whether in chemistry or in any other subject. The author believes that this method of making out the final grade is fairer to the students than the ordinary "averaging" method in courses where, by the nature of the work, the numerical averages of the different units for the whole class are not the same. I t has been his experience that students, to whom the system has been explained, comment upon what they choose to call the "fairness" of it.
