Written Tests of Laboratory Skills Albert G. Krieger Jackson Community College, Jackson, MI 49201 Althouah most lahoratorv work is evaluated hv instructor evaluation of student reports, a few colleges are adding alternative methods, that of administerine laboratorv nerformance tests (I),grading student evaluati&s of unknowns (2), observations by teaching assistants (31, and paper-pencil lahoratory tests (4). Kruglak (5) concluded from his studies of performance tests that "paper-pencil analogs" might be designed to evaluate very specific skills from the laboratory. If i t were possihle to construct paper-pencil items that were highly correlated with parallel laboratory performance tasks, then measurements of some lahoratory skills would be improved. This study tries to answer the following questions: (1) Is there a difference hetween a multiple-choice written test using photographs of equipment and scales and a parallel multiple-choice laboratory performance test (hereafter referred to as LPT) that utilized actual equipment.? (2) If two lahoratory tests are taken in succession, which will produce the greatest practice effect on the other, the LPT or the written test? Test Construction The tests were intended tomeasure the ahilitv of students t o t.xtnlv1 \.Cry apeciiir infcmn;itiun trim i~lslrul~ie~it. .,nd ur rr:~!h*:r l I the unit. heine iiit~:r~un~l. 121 r h leas1 ~ :;iih~ ci11bration, (3) the smallestmeasurement discernible, (4) the relative error of measurement, (5) the magnitude of the measurement exhihited, (6) the percent error of the measurement made, and (7) the number of significant fiaures in . the measurement. Measurements of quantities were limited to obtaining information from graphs and from laboratory instruments of the following types: burets (volume), single-pan and triplebeam balances (mass), barometers (pressure), glass thermometer (temperature), pH meters and multimeters (electrical potential), ampere-meters (electrical current), colorimeters (optical absorbance and wavelength), and stopclocks (time intervals). In 1 ~ 1 tcase= h lht! ~n~~ltiple-choice answers were m l c r randmized. The wrilteil~vdhxl nu rime i~mil.but in iiocast'did the test take more than 55 minutes. The LPT was constructed as nearly parallel to the paper-pencil test as possible, but there were differences in laboratory instrumentation styles and scales and in the order of the randomized answers. Six minutes was , ~ l l t ~llt,r t d in~rrumentper stwIt.nt for a total rdH; ini~iute, iclr the cc~mpltriunoft he entire test for 1wh r t ~ i d e ~ i1 8t1. both cases the maximum possible raw score on the tests was 60 points. Test Sample and Population The test sample consisted of thirty-four students in Chemistry 152, General Inorganic Chemistry With Analysis, Paper-Pencil and Laboratory Perlormance Test Comparisons Test Order
N
Group 1 Group 11
17 Lab Pelformance (first) 17
Paper-Pencil (second) Paper-Pencil (first) Lab Performance (second)
Mean
Correlation
0.7V
35.6
6.88
41.2 38.4
7.72
39.1
5.38
'Significant at the one-percent level 230
S.D.
Journal of Chemical Education
6.75
0.73'
a second-semester course for freshman students in chemistrv. engineering, pre-medical, pre-veterinary and pre-dental curricula. The lecture text ( 6 ) was the one in widesaread use while instructor handouts and lahoratory separates ( 7 , 8 )were utilized in the lahoratory. The students ordinarily worked alone in the laboratory and submitted a weekly report, which was graded by the laboratory instructor. d ,
Test Administration and Data Analvsis The experimental tests were administered during the next to last lahoratorv weriod scheduled during the winter semester ~~~~of 1977-1978.0; the day of the tests, theyahoratory instructor divided the section by randomly assigning one-half of the students (who had been match-paired for ability on the basis of test and laboratory work completed) to the paper-pencil test. The LPT was simultaneously taken by the other one-half of the students. During the second half of the period, the testing procedure was reversed so that all students took both tests. The means, standard deviations, and correlations between the LPT and the written test scores mav be found in the data table. A t-test for dependent scores was performed on the scores of both groups and no significant difference was found (P. 01). This result implies that only random differences exist hetween the scores obtained by the two tests. A practice effect was more pronounced when the lahoratory performance test was administered first. The product-moment correlation coefficients are very nearly the same and are significant at the one percent level. ~
Discussion It was found to be extremely difficult to maintain particular magnitudes on the instrument scales when set to the test specifications. The students were also prone to adjust whatever dials, knobs, sliders, or whatever devices there were to be adjusted, even though the students had been instructed to merely read the scales without making any adjustments. These instructions were given because it was felt that such adjustments would introduce an additional variable into the skills measurement that would not he easily measured on the written test format. In addition, pH meters and other instruments undergo meter needle drift and require frequent readjustment. The lahoratory illumination was generally good so that the calibrations were easier to view on the actual instruments. Redicate test stations would have made the administration of the L P T easier and more economical but were not utilized due to a lack of identical a~waratus. Reliabilitv was deter.. niined 1111 h ~ht t o r i~,rmi.TIit' tiuder HirI~:irdi~w tilt-21, 111 t he paper-IWIIC 11 tt>>twa. u.& !vInl( I hc I< I< ? t
