application the tests are learning devices and not instru- ments of ... Each item has a short interactive tutorial addendum to assist in the drill, ... software package in BASIC to run on an Apple II ..... ~-6 In them, the development of kinetic.
108
Microcomputer-based Question Bank for Training and Assessment in Biochemistry J L IBORRA, J A LOZANO, P TARRAGA and A REQUENA
Department of Biochemistry and Physical-Chemistry University of Murcia Murcia, Spain Introduction Usually, the large number of students involved in general courses of Biochemistry is invoked as an argument that an alternative procedure to the use of essay-type examinations is needed to evaluate student performance. Tests are widely accepted as being a first-class method of evaluating students' achievements. 1-6 The single answer, multiple-choice questions and the 'fill-in-the-blank' are the most common procedures used in such tests. Much effort has been applied in this direction. For example, a Medical Biochemistry Question Bank (MBQB) was produced as a resource for test generation. 7 The conjunction of computer and Question Bank provides an excellent tool for learning. The computer changes the scope completely and has some important advantages over the usual examination methods: not all the students have to answer the same questions, the delay in correcting the exercises is eliminated, and grading is immediately known. Moreover, in recent years, microcomputers have become much cheaper and more adequate for use in educational areas. However tests have other important purposes. They increase student comprehension and help the teacher to identify those concepts that should be re-taught. Certainly grades cannot be determined exclusively from these tests but they are an important tool in the total process of evaluation. It is obvious that scores should indicate those areas which need to be re-taught and those which were inadequately understood. Another interesting view of the test is the application to training, in which the students become aware that mistaken ideas will also receive attention. In this way, help is offered to encourage learning, giving students several chances to correct misunderstood concepts. In this application the tests are learning devices and not instruments of punishment for the inattentive. 8 Thus if an incorrect option is chosen, an explanation and several book references in which the topics are treated, are offered. As a result of this help each student sees that good grades can be obtained by anyone. The principal objective of this paper is to describe the use of a microcomputer question bank in an interactive tutorial way as a step before grading. Each item has a short interactive tutorial addendum to assist in the drill, and several books, including pages to consult about each particular incorrect response are offered. A complete software package in BASIC to run on an Apple II microcomputer was elaborated. An example of its application in the subject area of Enzymology is presented.
BIOCHEMICAL EDUCATION 12(3) 1984
Methods
Package description The information is stored on floppydisk (140 Kb) with the following distribution: - - one diskette for the programs, where the file with the lesson name and the book file are stored. - - one diskette for each lesson module. - - one diskette for each student course. To make access from one to another easier, the programs are linked.
General Menu Upon switching on the computer, the following menu is shown: [1] Question module [2] Exercise module [3] Assessment and exercises [4] References [5] Assessment scores [0] End of operation By pressing the appropriate key it is possible to access the desired block of programs. We shall now examine these in greater detail. Question Module The possible options are as follows: [1] Initialization of lesson diskette [2] Creation of modules [3] Consulting [4] Modification [5] Listing [6] Lesson name consult [0] End of operation The modules are distributed on diskettes, and we are able to store a maximum of 70 questions per diskette, which can be of three different types, A, B and C, as defined in Table 1. The maximum number of characters per question is 480, while the text for all the options cannot exceed 800 characters. Each question is marked with a degree of difficulty from one to three in increasing order.
Exercise Module The options to choose from in this case are: [1] Introductory comments [2] Consulting [3] Modification [4] Listing [5] End of operation The same diskette containing the question module for the assessment, also carries (a) an additional file allowing up to five references, and (b) one commentary for each question with a maximum length of 400 characters. The references are chosen from a maximum of 99 books, codified by numbers that are stored in the same file. The treatment for this additional file is made by the following programs (choosing the option 4 in General Menu): [1] Introduction to books [2] Consulting [3] Modification [4] Listing [0] End of operation
109 Table 1 Multiple Choice Questions: Types Used Type A Selection of the correct answer from five possibilities Type B Selection of the correct answer from five possible combinations: Choose (1) (2) (3) (4) (5)
If If If If If
a, b, c and d are correct a, b and c are correct a and c are correct b and d are correct all four are incorrect
Type C Selection of the correct answer from five possible combinations of an assertion and a reason: Choose (1) If both the assertion and the reason are true and the reason is a correct explanation of the assertion. (2) If both assertion and reason are true but the reason is not a correct explanation of the assertion. (3) If the assertion alone is true. (4) If the reason alone is true. (5) If neither is true. For each book there is an alphanumeric variable with a length of 70 characters, in order to be able to store the title, year, author(s) and publisher. Assessment and exercises Let us now consider the part corresponding to the carrying out of the examinations and exercises. By choosing option 3 in the General Menu the following is displayed: [1] Initialization of students diskettes [2] Assessment modules [3] Exercises [0] End of operation For the assessment, the number of questions is determined by the professor, with a maximum of 10 (can be increased), whereas in the self-training section this is set by the student. In this case, the questions are displayed in increasing order of degree of difficulty, beginning with the simplest, obviously. In student assessment the question order is established totally at random. Also, it is possible to select the maximum level of difficulty in the questions in this mode, and so, questions from the simplest to the most difficult are used. The question text and the options are displayed in two successive screens, the student being able to go from one to the other by pressing V on the keyboard. In the self-training mode, when the wrong answer is given, two additional screens appear, one containing textbook references with page numbers, from which the student can get information about the question, and on the other one, the comments by the professor on that question. When the student does not know the right answer, he can choose to offer no answer if he desires and BIOCHEMICAL
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if so this question is not taken into account in the marking. When the student has finished he receives a print-out giving the correct answers compared with those given by him, and his mark. In the display, only a count of the questions answered correctly, incorrectly and not answered appears on the screen but no mark is given. The assessment program contains a time counter that tells us the time spent by the student in answering each question. This time can be related to other variables such as degree of difficulty, discrimination capacity, etc, in the statistical treatment of results. Assessment scores Finally, a results menu is incorporated to obtain data about students. On choosing option 5 in the General Menu the following is displayed: Result [1] from one student (monitor) [2] from one student (printer) [3] from one lesson module (monitor) [4] from one lesson (printer) [5] from one course diskette (monitor) [6] from one course (printer) [0] End of operation Each student's diskette corresponds to one course, it being possible to store as much as 600 students per diskette. For each student, the following data are stored: name, date of examination, lesson module of examination, and, for each question: type (A, B, C), difficulty level (1, 2, 3), correct answer option, student's answer option, and answering time. Statistical analysis
A statistical analysis of the tests is very useful in validation as well as teaching and learning processes. The following statistics are incorporated in validation menu: - - Number of students taking the test - - Class mean (average) - - Range of test scores - - Difficulty of each choice in each item - - Difficulty of each item - - Discrimination index of each choice in each item - - Discrimination of each item A first difficulty degree is assigned to each item when it is put in the Bank and the results obtained successively permit the correction of this first assignation. The minimum number of students necessary for meaningful item analysis would be about 20-30 students. Since the score, the time spent in each item, and the student's response and date, are stored for each student in each lesson diskette, the above statistics can be calculated. For any given test or examination, the mean and range are defined as follows: mean = sum of all scores/total number of scores range = difference between the highest score and the lowest score. The item analysis is very helpful to the teacher in order to evaluate the quality of instruction and the reliability of
110 each item. The sequence followed to obtain item analysis data for a test is: (1) The results are ranked from the highest to the lowest score. (2) If the total number of answers is quite large, the first 25% (high group) and the last 25% (low group) of the answer sheets are taken and fifty tests from each group are randomly chosen for the calculations. (3) If the total number of answer sheets is between fifty and ninety, the highest 25 tests (high group) and the lowest 25 (low group) sheets are used. (4) If the total number of answer sheets is less than fifty, the upper (high group) and lower (low group) halves are used. These data are now used to calculate the difficulty and the discrimination indexes. The difficulty of each choice is the percentage of students responding to that choice: Difficulty = (number of correct answers in the high group + number of correct answers in low group)/total number of test used The degree of difficulty (as a percentage) of the correct choice is the difficulty of each item. The difficulty of the other incorrect choices indicates the degree of attraction of each choice and if one of the options has been chosen by a very small percentage of students, or not selected at all, it might indicate that a distractor should be substituted in this item. The discrimination index of each choice in each item allows us to discriminate between students in the high group and students in the low group. Discrimination index -- (number correct in high groupnumber correct in low group)/t/2 total number of tests used. A positive discrimination index indicates that this item is useful to discriminate between students included in the high group and students considered in the low group. A negative result brings just the opposite conclusion. The discrimination index for the correct choice is the discrimination index of each item. These results enable us to readjust the quality of items when used in subsequent examinations. It is a very important tool to increase our abilities to handle tests adequately. Question B a n k in General Biochemistry
The Question Bank for self-training and assessment in Biochemistry has a series of modules: - - Structure of Cell Components - - Enzymology - - Metabolic Generation of Energy of the Cell - - Storage of Fuel and Biosynthesis of Biomolecules - - Metabolic Regulation - - Genetic Biochemistry - - Biochemistry of some Biological Processes The questions correspond to a program of General Biochemistry at Murcia University. Obviously, Spanish is the language of the user. BIOCHEMICAL
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The Question Bank is included as part of a greater educational experiment that is currently being developed at the University of Murcia, consisting in a CAI project of a Biochemistry curriculum that employs Apple PILOT as programming language and Applesoft for testing and simulation. The assessment and self-training steps are carried out using the Bank as explained in this paper. It would be premature to offer an evaluation of our experience with this learning experiment but the preliminary conclusions are hopeful. As examples of the contents of items in the Question Bank for self-training, three questions on enzymology are presented, as they are displayed by the microcomputer, along with the comments and recommended references. Type A item Invertase is an enzyme showing MichaelisMenten kinetics. How many times should substrate concentration be increased to change the reaction rate f r o m 1/3 V m to 2/3 Vm? (1) Twice (2) Three times (3) Four times (4) Nine times (5) None of these Correct answer: 3 C o m m e n t : If the ratio of velocities for V~ = V3 Vm and V2
= 2/3 V,,, is established, the ratio $1/$2 is obtained. References
Lehninger pp 198-199; Stryer p 121; White pp 205-206. Type B item With reference to enzymes is it TRUE that: (a) Their catalytic power depends on providing a reaction pathway of lower activation energy than the uncatalyzed reaction? (b) The rate of an enzyme-catalyzed reaction is dependent on temperature? (c) The Km represents the molar concentration of substrate which gives half the maximal velocity for a given concentration of enzyme? (d) All enzymes operate optimally at neutral pH? Correct answer: 2 [see Table 1] C o m m e n t : Most enzymes have a characteristic pH at which their activity is maximal. The optimum pH is not necessarily identical with the pH of the normal intracellular surroundings. References
Lehninger pp 198-199; Stryer p 121; White pp 202-220. Type C item The multiple forms of a given enzyme catalyze the same reaction BECAUSE all of them are isoenzymes. Correct answer: 3 [see Table 1] C o m m e n t : Enzyme multiplicity cannot be assigned only to gene multiplicity which codes the primary structure of
111 protein: postranslational modifications of enzymes may also be involved.
References Lehninger pp 200-252; Stryer p 374; White p 378. References 1 Cox R (1972) Nature 237, 489-492 2 Smart C A (1976) Br J Hosp Med (Feb issue) 131-136 3 Hubbar J P and Clemans W V (1961) Multiple Choice Examinations in Medicine, Lea & Febiger, Philadelphia 4 Lennox B (1974) Hints on the Setting and Evaluation of Multiple Choice Questions of the One-from-Five Type, Association for the Students of Medical Education. Dundee Medical Education. Booklet No 3 5 Matthews J (1977) The Use of Objective Tests, University of Lancaster School of Education. Teaching in Higher Education. Series No 9 6 Morgan M R J (1979) Biochem Educ 7, 67-69 7 Peterson J A, Agee C C, Baggott J, Bentley J P, Fairley J L, Rawitch A B and Stillway L W (1982) Biochem Educ 10, 16-18 8 Lee A E and Mayer W V (1971) Resource Book of Test Item for Biological Sciences: Molecules to Man, Biological Sciences Curriculum Study. Boulder, Colorado
we include the theoretical basis to explain how the rules were deduced; then the rules are given in order to obtain the velocity equation whose derivation is shown in the previous section. Finally, the application of the rules to solve some typical examples is included.
A: Theoretical considerations Before giving the practical rules for writing the enzyme velocity equations under rapid equilibrium assumptions, let us explain the theoretical basis from which they arise. We shall consider first the simplest case when only one effective complex is involved, and later we shall consider the general case when two or more effective complexes are present at the same time. (i) With a single effective complex. Let us consider the case of a random bireactant system as indicated below: Ka E+A +
EA +
B
B
f
Editor's note: The authors have expressed interest in exchanging programs with others. Anyone interested should write directly to them.
Scheme I
A Rapid and Easy Method for Writing Enzymatic
Velocity Equations Assuming Rapid Equilibrium Conditions JUAN L SERRA and RAFAEL SAIZ Departamento de Bioquimica Facultad de Ciencias Universidad del Pals Vasco Bilbao, Spain
Introduction Although the concepts and theoretical assumptions of enzymology are relatively simple, the derivation of enzyme velocity equations (which may appear somewhat complicated at first sight!) inevitably involves a certain amount of mathematics. Indeed, most of the calculations are elementary and the derivations usually follow on the basis of simple logic, the apparent difficulty arising more from the necessary abundance of terms and profusion of symbols than from any real conceptual difficulties. When students try to derive, by themselves, enzyme catalysed velocity equations, following either steady-state or rapid equilibrium assumptions, they find the job in some cases tedious, often cumbersome and always time-consuming. There are a large number of excellent textbooks on enzyme kinetics available for undergraduates and graduate students, and some of them are included here in the reference list. ~-6 In them, the development of kinetic equations is often done in such a way that sufficient steps are detailed in order that most readers would be able to follow the derivations despite their possibly limited mathematical backgrounds. The purpose of this paper is to give some practical rules which allow the systematic development of velocity equations without involving any calculations at all. First,
BIOCHEMICAL EDUCATION 12(3) 1984
f EB + A
Ka
k EAB
f
E+P+Q
where E, A and B represent the free form of enzyme or substrates, EA, EB and EAB represent the binary or ternary enzyme-substrate complexes, Ka, Kb, K'a and K'b are dissociation equilibrium constants, and k is the catalytic rate constant for the appearance of products (P and Q). The values of the dissociation constants are given by: [E] [A] g a - [EA] (1)
Kb - [E] [B]
[EB]
(2)
[A] [EAB]
(3)
K'b -- [EA] [B] [EAB]
(4)
K'a
= [EB]
Using the above definitions we can express the concentration of each enzyme species in terms of [EAB], the single active form of the enzyme. Thus: K.
K'b [EAB]
[El - [A] [B]
-
K'.
Kb [EAB]
[A] [B]
(5)
[EA] = K'u [EAB]
(6)
[EB]- K'a [EAR]. [A]
(7)
and
