MEASURING the ABILITY to INTERPRET EXPERIMENTAL DATA* F. P. FRUTCHEY
AND
R. W. TYLER
The Ohio State University, Columbus, Ohio
B. CLIFFORD HENDRICKS The University of Nebraska, Lincoln, Nebraska
T
HE American Council of Education through its for another of the less tangible but desired outcomes of Coijperative Test Service is helping college teach- chemistry instruction. ers to become more critical of their examinations. Teachers of chemistry are interested in helping their In science, expression of that need for more adequate students interpret data obtained from experiments new tests is voiced in such statements as: "Skilled help is to the students. This constitutes one of a variety of needed by the teacher in building tests for such in- objectives of the teaching of chemistry. This objective, tangible objectives as ability to infer, ability to use the when expressed in terms of the behavior of students, scientific method of thought, and ability to apply the often means that when students are presented with exprinciples of chemistry."' College teachers are also perimental data new to them, they will formulate and rekamining their aims in an effort to he sure for just state interpretations which may reasonably he made what they should test.% Some provisional test forms from the data. Various kinds of experimental data, have been suggested for the application of principle^.^^^ such as tabulations, graphs, and qualitative statements, be presented to the students and in such an exThis -paper is reporting an attempt to provide a measure may 'Presented at the eighty-ninth meeting of the American amination they may be expected to react to each set of Chemical Society before the Division of Chemical Education, data in turn. Since the objective is to teach students New York, April 26,1935. 0. M. S ~ TAND H B. CLW~ORD HENDRICKS, "Service tests for to interpret data which are new to them, data with which students are unfamiliar must be presented. One chemistry," Sch. Sci. Math., 35,48&91 (1935). 0.M.SMITH, "Accepted objectives in the teaching of general source of these data consists of recent chemical litera12, 1803 (1935). college chemistry." J. CHEM.EDUC.. FRED P. FRUTCHEY, "Measuring ability to apply principles of ture containing the reports of chemical experiments. chemistry," Educ. Research Bull.,12, 255-60 (1933). This precaution precludes the possibility of parrot-like ' B. CLIFFORDHENDRICKS, RALPHW. TYLER, AND FRED P. repetition of memorized interpretations and makes i t FRUTCHEY, "Ability to apply chemical principles," J.~CHEM. necessary for the students to formulate their own interEDUC., 11, 611-3 (1934).
pretations. Some students can repeat from memory interpretations which were made for them but cannot interpret new data for themselves. Other students, who do not know and cannot repeat interpretations which others have made, can make reasonable interpretations if given the experimental data. The achievements of students are quite different in different objectives of teaching. To obtain a clear, comprehensive picture of the students' achievement in chemistry i t becomes necessary to collect evidence of achievement in each of the important objectives of chemistry teaching. The behavior expected of students in interpreting experimental data is their own formulation and statement of interpretations. Two examples of the kind of exercise used to collect this evidence are given below. TYPE I TEST PORM
Directions: I n each of the exercises on the followim... pages an experiment is described. Read the description of each experiment. Assume that the facts given in the description of theexperiment and in the results obtained are correct, then an the basis of these facts only write the conclusions you could reasanably draw from the results obtained in this experiment. A. an experiment some white starch was treated with brown iodine solution. This was done ten times and each time a blue color was formed. Later some white starch was mixed with saliva. The mixture was left for a time and then treated with brown iodine solution. This was done ten times and each time no blue color was formed. Write in the space below the conclusions you could reasonably draw from the results obtained in this experiment. B. Sixty plates of the same size were cut from a piece of blue annealed tank steel. Twenty plates were coated with zinc t o a thickness of 0.007 inch; ten of these were placed in 200 cc. of gasoline and 25 cc. of distilled water containing 1 of powdered sulfur, and ten in 200 ec. of gasoline 25 cc. of sea water. Twenty plates were coated with cadmium to a thickness of 0.007 inch; ten of these were placed in 200 cc. of gasoline and 25 cc. of distilled water containing 1 gram of powdered sulfur, and ten in 200 cc. of gasoline and 25 cc. of sea water. Twenty plates were not coated; ten of these were placed in 200 cc. of gasoline and 25 cc. of distilled water containing 1 gram of powdered sulfur, and ten in 200 cc. of gasoline and 25 cc. of sea water. The corrosion deposited on each of the 60 plates over a period of 7 days was carefully weighed and the results were tabulated as follows: Cromr of c o r r o s i a on S k d PInics Cookd with Zinc Cadmium Nof Coofrd Ga~olinewith sulfur Ga~olinewith sea water
0.0936 0.9966
0.0060
0.0250
0.1126 0.1958
Write in the space below the conclusions you could reasonably draw from the results obtained in this experiment.
A oradical oroblem is immediatelv encountered in evidence of achievem~nt, ~h~ method col&ctmg is time-consuming. It takes considerable time for the students to formulate and write their own interpretations and usually three readers to grade the students' interpretations. We have been developing and trying out several methods to overcome these two difficulties. The first
method we tried consisted of exercises like the following. TYPE I1 TEST FORM
Directions: I n each of the exercises below several facts are given. After the facts, are suggested a number of inferences. Assuming these facts are true, select the inference which seems to you most reasonable and place a check mark on the blank line. A. I n an experiment some white starch was treated with brown iodine solution. This was done ten times and each time a blue color was farmed. Later some white starch was mixed with saliva. The mixture was left for a time and then treated with brown iodine solution. This was done ten times and each time no blue color was formed. a. Saliva turns starch to sugar.. ............ b. Saliva turns iodine blue.. .................. -b. c. Saliva produces a change in starch. ........ .LC. d. The color of saliva destroys the blue color.. e. Saliva has no effect on grape sugar. ........ e .
The students are expected to select the best interpretation of those givenand check it. This did not prove so however. a group of students an examination composed of a variety of experimental data and formulated their own interpretations, and immediately afterward took the new examination in which the students were expected to select the best interpretation of the same data, the two sets of results did not parallel each other closely, The relationship expressed by the coefficient of correlation was .38. A second method was' then considered. This consisted of having the students select from a list of five possible interpretations, and mark in an appropriate wav. < . the most reasonable and most coniolete intemretation of the data and the tradicted by the data given. An example of this kind of exercise is given below.
men
Gon-
TYPE 111 TEST PORM
Dimclions: I n each of the exercises below, an experiment is described. Below the description of the experiment are given several statements which have been suggested a s interpretations of the experiment. Assume that the facts given in the description of the experiment are correct, then on the basis of these fads onlv select the statement which seems t o vou the most reasonable and most conaplcte interpretation of thew facts and place a n Y after it. Sonw of the statements are poor interpretations hecause they incompletely interpret the facts given or are partly or wholly contradicted by the facts given. Select the statement which you believe t o be contradicted by the facts given and place an 0 after it. A. Starch when treated with iodine solution gives a blue color. When saliva is mixed with the starch and left for a time the mixture no longer turns iodine solution blue. ~~
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a. Saliva and iodine do not mix.. ............ -a. b. Saliva t m s iodine blue.. ............... c. Saliva produces a change in the starch.. .... X c . d. The color of saliva destroys the blue color.. ._d. e. Starch mixed with iodine solution does not turn blue.. ................................. O e .
When this method was checked with the original method in which students formulated their own interpretations, in the, same way as described above, the two sets of results paralleled each other more closely.
The relationshiv emressed bv the coefficient of correla* tion was 3 5 . A third method was thought to have further promise in that it may yield results which are still more similar to the first method and that i t would show whether students can discriminate between three kinds of interpretations. Examples of this kind of exercise are as follows. A
TYPE N TEST RORM
Directions: I n each of the following exercises, an experiment is described. Below the description of the experiment are several statements which have been suggested as interpretations of the experiment. Assume that the facts given in the description of the experiment, and in the results obtained, are correct, then on the basis of these fads only consider each statement. Mark with a l-every statement which is a reasonable interpretation of the results obtained. 2-very statement which might possibly be true but for which insufficient facts are given to justify the interpretation. 3-verY statement which cannot be true because it is contradicted by the results obtained in the experiment. A. I n an experiment some white starch was treated with brown iodine solution. This was done ten times and each time a
a. Coating the steel plates with cadmium was more effective in preventing corrosion than was coating with zinc.. ................... .(l)a. h. I n the gasoline containing sea water more corrosion was formed on the steel plates which were not coated than on the zinc-coated steel plates.. ................................ .(3)h. c. Coating pig iron with cadmium reduces the amount of corrosion formed on pig iron.. ... .(2)c. d. More corrosion was formed on the uncoated plates in the gasoline containing sulfur than in the gasoline containing sea water.. ...... .(3)d. e. The distilled water corroded the coated and uncoated steel plates.. ................... .(2)e. f. I n the gasoline containing sulfur, the uncoated steel plates contained more corrosion than the zinc-coated steel plates.. ...............(l)f. g. I t is more expensive to coat steel with cadmium than with zinc.. .................... (2)g.
The students are expected to mark with a 1 the reasonable interpretations justified by the data given, to mark with a 2 the interpretations which might be true but are not supported by the data given, a i d to mark with the contradicated by the data
given. Although so far as we have been able to discover, this kind of exercise did not increase the degree of h1.m fnnnea correspondence with the original method in which ..... ,.,,lnr Later some white starch was mixed with saliva. The mixture students formdate their own interpretations, i t does was left far a time and then treated with brown iodine solu- help to find out whether students can discriminate betion. This was done ten times and each time no blue color tween three kinds of intmretations. was formed. To those who assume ;hat a student who has aca. The starch was changed to sugar by the action of quired a large fund of chemical information has also saliva.. .................................@)a. made the same degree of achievement in b. Saliva digested the starch.. ..................(2)b. new experimental data, this work may appear to be c. Starch acted upon the iodine.. .............. .(l)c. d. Saliva produced a change in the starch.. ...... (1)d. unnecessary. We have checked that assumption. e. Starch mixed with iodine solution did not turn Students who have acquired a large fund of information blue.. .................................. .(3)e. have not always the same deeree of success in interB. Sixty plates of the same size were cut from a piece of blue preting n e eaperimental ~ data, In various fields the annealed tank steel. Twenty plates were coated with zinc relationships expressed by the of to a thickness of 0.007 inch; ten of these were placed in .27 .60. We have stu200 cc. of gasoline and 25 cc. of distilled water containing 1 ranged pram- of . oowdered sulfur. and ten in 200 cc. of easoline and 25 dents who are eood a t memorizine facts and orincioles cc. of sea water. of a subject cannot always use that information with Twenty plates were coated with cadmium to a thickness of equal success in solving problems, various 0.007 inch; ten of these were placed in 200 cc. of gasoline and 25 cc. of distilled water containing gram of powdered fields the relation between these two objectives ranged from .31 to .58. Likewise, students who are good a t sub, and tenin200 cc. of gasoline and 25 cc. of sea water. Twenty plates were not coated; ten of these were placed in using memorized information in solving new problems 200 cc. of gasoline and 25 cc. of distilled water containing 1 are notalways good at interpreting new experimental gram of powdered sulfur, and ten in 200 cc. of gasoline and data. The relation between these two objectives 25 cc. of sea water. The corrosion deposited an each of the 60 plates over a period ranged .33 .54. The results, obtained by checking the achievement of 7 days was carefully weighed and the results were tabulated as follows: of the same students in different important objectives of teachine, indicate that in order to have a clear. comcrams of c m o r i o n an stera platrr - ~. C O ~&hI ~ ~ prehensivepicture of the growth of students as a'result ZilC Cndmium No1 Cooad of teaching, it is necessary to obtain evidence in each Gasoline with sulfur O.Og30 0.0000 0.1126 oaso~inewith sen rater 0.9966 o.ozso 0.1958 of the important objectives of teaching.
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Philosophers may be right i n afiming that wc cannot trancend expcricncc:
we can, nf all euents, carry it a long wayfrom i f ~ o r i g i n .
We e m magngy, diminish, qualify, and combine expcricncm, so as to render them fit for p r r r p o . ~enfimly new. I n ecsplaining jensiblc l o j the ultm-~cnsiblc. There are Tories emn i n cicnce who regard Imagination ar afaeulty phenomcnn, wc habitually form m ~ n f n images to be jrarcd and avoided rathrr than cmployrd. They haw obnrvcd it^ adion i n weak v e r d s , and are unduly impressed by its dim+ fcm. But they might with c q u a l j u ~ f i c cpoinf to exploded boilers ar a n nrgumcnf against the u ~ o ef steam. With accurafe cspcrimcnt and obrer~ntionto work upon, Imagination becomer fhc nrchifcef o j p h y ~ i c a ~ l ~CO~~.-TYNDALL
