I
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I
Ardas Ozsoaomonvanl Skyline College San Bruno, C A 94066 and Drew Loftus2 University of California
Preciictors of General Chemistry Grades
Chemical educators have a sustained interest in identifying accurate nredicton of colleee chemistrv erades. New variahles. such as cognitive styles (1)and piage;& levels of intellectual development (2,3)are being studied as potential predictors in addition to the traditional ones which include, among others. hieh school chemistry mades (41, math SAT scores (51, and gridei earned in a preparatory course to college chemistry (6).This paper describes a study conducted a t U.C. Berkeley during 1976-1977. The population under study consisted of the students enrolled in Chemistry 1A during fall 1976. Chemistrv 1A is the first ouarter of a vear lona- "eeneral chemistry course. During each fall quarter, approximately 1500 students enroll in Chemistry 1A. The course is taught in the traditional lecture-discussion format with two 1-hr lectures. one 1-hr discussion. and one 4-hr laboratorysession per week: Frequently wed teutbooks arc Pimrntel and ~ p r a ~ l e y ( 7 ) and Milhan (X).'l'hisstudy u,ascundurted tor the purpose of identiiving those variables that muit ac~uratelywuuld predict wurse grmles utilizing a rrgressim equation. As part of anuther study, one 01' us (A.0.) de\.eln,ped a sham rhrmistry prrte4t ibr the purpose of identifying underprepared students whu wen. enrollcd in Chtm IA ( 9 ) .'l'his test, ulonp. with two questions on algebra (see ~ a h l ' e1) was administered to all students enrolled in Chem 1A during the first week of classes. The scores on the chemistry and algebra questions were recorded separately and are identified as chemistry pretest and algebra pretest scores in this paper. Five independent variahles were studied as potential predictors of Chem 1A grades, the dependent variable. Although
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the total enrollment in Chem 1A was 1502, complete information for each student on all variables was not available. The independent variahles were (the numbers of students for whom the value of a particular variahle was known are given in parentheses): completion or noncompletion of high school chemistry ( N = 1039); high school chemistry grade (N = 1020): chemistw Dretest score ( N = 1439): algebra ~ r e t e s t score ( N = 1434;and math scholastic aptitudetest (hereinafter referred to as math SAT) score ( N = 1148). There were 773 students for whom complere data wen, availal)le. Simple correlation coefficients hetween (:hem LA pradri and w x h of the four variables (excludingthe first one) &re calculated and found to he as follows: for high school chemistry grade, r = 0.3766:, for -~~ chemistrv nretest score. r = 0.4158: for aleehra pretest score, r = 0.2121; and for math SAT score, r = 0%071. In addition, the correlation coefficient between Chem 1A grade and the final exam score was also calculated and found to he r = 0.8665, indicating a strong contribution of the final exam score to the course grade. The grade distribution of students who completed high
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Table 2. Chem 1A Grades versus High School Chem Grades Hioh School Chem Gradee Cham 1A Grade
1 Work undertaken while this author was completing his doctoral studies st U.C.Berkelev in the Graduate Grour, in Science and Mathematics Education. ~orrespondeneeshould be addressed to this
C (%)
A
1.8 N = 57
Column Total
author.
A 1%)
None
5.1
20.7
N = 356
N = 545
4.5 N = 88
B 1%)
1%)
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2
Present address: NYU Medical School, 550 First Avenue, New
me lasf column show9 the Chem 1A grade distribvtion of studens wim no high schwl chemistry.
York, NY 10016.
Table 1. Chemistry and Algebra Pretests Lab section
Name (please print)
Phone No.
Lab room
Did you complete high school chemishy Chemistry 1A Pretest (10Minute Limit) PLEASE BE SYSTEMATIC AN0 SHOW ALL YOUR STEPS
Atomic weights you will need are: H = I;N = 14.
1. a. (1 !mint) What is me molecular weight of NH,? Show your work. b. ( 3 points) How many moles of NHs are mere in 8.5 g of NH,? Show your work.
ans: 2.
(4 points) How many moles of A1,03 can we prduce by macling 5 moles of aluminum with excess oxygen? The reaction is: 4AI
+ 30, -
3.
-
I
I
2AhO3. Show your work. any
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(2 points)Balance the fallowing equation: N2
+ HZ
-
I
NHs
.
For que9fio11s 4 and 5 below, circle the correct answer. Do note use a slide rule ru calculator. (A raised dot means "times;" thus "7 11" is seven times eleven).
270 X
4.
(5 points) 5.6 =
5.
(5 paints) x- 5.102 = 7.6
lo3
x=3
8.1
9
8100
none of these
x=3
8.1
9
8100
none of these
Volume 56, Number 3, March 1979 / 173
Table 3. Chem 1A Grades versus Math SAT Scores Math SAT Swres Chem 1A Grade
200-449
DorF
C+. C, or CAorB Column Total
450-499 (%)
500-549
(%I
650-899 (%)
700-749
(5)
550-599 (%)
600-649
(%I
1%)
750-800 (%)
42.2 53.3 4.4 N=45
12.1 80.3 7.6 N = 66
14.8 71.1 14.1 N = 149
8.0 76.6 17.4 N = 201
3.8 56.3 39.9 N=238
3.4 47.6 49.0 N=206
1.4 34.0 64.6 N = 144
1.6 24.2 74.2 N=62
school chemistry and of those who did not is shown in Tahle 2. The dropout rates of the students in the two groups (not shown in Table 2) were significantly different: 5.0% of students with high school chemistry dropped whereas 15.6% of the others did so. The Chem 1A grade distribution versus math SAT scores were computed (see Tahle 3). In this table the de~endenceof Chem 1A grades on math SAT scores is examined in great detail byconsidering the SAT scores in increments of 50 for the three Chem 1A grade categories. Multivariate Analysis Examination of availahle data indicated that math SAT scores. chemistrv Dretest scores. and hieh school chemistrv grades'were like$ be the best predictors of Chem 1A course grades because these predictors correlated well with the dependent variahle. It was decided to carry out a multivariate analysis using those predictors and taking into consideration only those students for whom complete data were available. There were 773 such students. Cbem 1A grades excluded from consideration for this analysis were: drip, pass, and incomplete. Table 4 shows the mean and the standard deviation of various variahles for the 773 students. In this table, the high school chemistry grades are represented by four "dummy" variahles. For example, if a student had a grade of A in high school chemistry then he was assigned 1 as the value of the A-dummy variable and 0 for each of the remaining dummy variahles. Predicting the Chem 1A grade of a student was accomplished by using all independent variables (see Table 4) combined. When this was done, the unstandardizedregression equation was found to be
where xl represents math SAT score, xz represents chemistry metest score. and the remaining letters renresent hieh school chemistry grades (none means high school chemistry). The dependent variahle Y represents the Chem 1A GPA. The standardized regression equation has the following coefficients: 0.39 for XI, 0.18 for x2, 0.21 for A-dummy, 0.02 for R-dummy, -0.04 for C-dummy, and zero for no-highschool-chemistry dummy. These coefficients indicate the relative imoortance of the contributions made bv the variahles in predict& the Chem 1A grade. The multidle correlation coefficient is R = 0.59 and R2 = 0.35. Thus. 35%of the variance observed among the students can he explained on the basis of the math SAT scores, chem pretest, and high school chemistry performance. Further analysis of data revealed that the combination of math SAT scores with chem pretest scores (R2 = 0.31) or the combination of math SAT scores with high school chemistry grades (R2 = 0.33) can account about equally well for the exnlainable variance. As part of t6e effort to counsel the Chem 1A students, expectancy tables were developed. One of these is displayed in Table 5. This table was constructed utilizing the regression equation and shows the probabilities of getting various average Chem 1A grades depending on performance in high school chemistrv, math SAT scores, and chemistrv retest scores. Three aspects of the regression equationare interesting to note (1)
Table 4. Complete Data on 773 Chem 1A Students
Chem 1A gradea Math SAT score Chem Pretest Adummy Mummy Cdummy No high school chemistry amis
Standard Deviation
Mean
Variable
2.41 610.4 7.61 56% 33 % 4.8% 6.2%
0.88 91.9 3.16 nla
n/a nla nla
isthe deoendentone
The contribution of "no high school chemistry" to predicting the Chem 1A grade is zero. For such students, the prediction is based only on the math SAT scores and the chem oretest scores.
The contribution of a C grade in high school chemistry to predicting the Chem 1A grade is asubtraetive one. This means that, in the population under study, students with no high school chemistry and who completed Chem 1A fared better than those who had a C in high school chemistry and also completed Chem 1A. (3) The contribution of a B grade in high school chemistry to predicting the Chem 1A grade is very small when compared to the contribution of a made of A. Of the four dummvvariables. only the A-dummy contributes significantly to thkprediction of the Chem 1A grade. (2)
Table 5. Average Grade in Chemistry tA by Performance in Hlgh School Chemistry, Score on the Chemistry Pretest, and Score on the Mathematical Section of the Scholastic Aptitude Test (SAT)a .... .. - . Score on the Chemistry Pretest
0-3 4-9 10 Subtotal (numbers)
Received an A in High School Chemistry
CC C
(200-549) 30.4% 30.4% 39.2% (56)
SAT Score (550-699) C 10.8% C+ 23.7% B65.6% (279)
'
Performance in High School Chemistry4 Did Not Receive an A or Did Not Take High School Chemistry
' B
B+
(700-800) 3.7% 12.8% 83.5% (109)
' IX CC
(200-549) 45.5% 25.6% 28.9% (121)
SAT Score (550-699) C20.2% C+ 31.4% C+ 48.4% (188)
d
&
(700-800) 20.5% 17.9% 61.6% (39)
Based on 792 stvdeMs fa whom me values of all mree independentvariables were known. 'This table separates sMsnts IMo Mn, goups an the basis of high Jdaol chemisby pdormance because an A grade In high school ohmisby is me strongest cmribvmlo me regennim equation when compared to mhw grades in high school chemistry. "This column shows me average Chem 1A grades of oludents whose mam SAT ecaes are shown on the adjacent column. *Average Cham IA gads was not computed because there were fewer man 10 students in this oategay.
174 1 Journal of ChemicalEducation
