Freshman Chemistry as a Predictor of Future ~cademicsuccess J a m e s S. Rixse and Miles Pickeringl Princeton University, Princeton, NJ 08540 Several studies have identified the score on the math SAT as the best predictor of suhsequent performance in freshman chemistry courses2-4, but what predicts success in organic predict chemistrv, and how well does freshman chemistrs . . grades in othrr science courses and sl~ccesiin entering medical srhool? We havr tried to answer these questions hv fdlowinp a group of students through their four years a t Columbia University and correlating various measures of their performance. Method Grades and SAT data were obtained for all 254 freshmen enrolline in freshman chemistrv a t Columbia Colleee. .. . the all-male undergrndunte division of ('olumhia University, in the fall of 1978. The overwhelmine maioritv of these students are premed since engineers enroll h t h l ~cl;oolof Engineering from the beainninr! and onlv a tinv minoritv goes on in pure science. ~ e freshLen w tak; biolo& or phy& concurr&ly with freshman chemistrv because of Columbia's other requirements. The raw grade data were converted to a numerical scale (A+ = 13, A = 12,. . . F = 0) and in all cases were "corrected" by subtracting the course mean. Thus a student who obtained a grade of B in acourse with a mean of 8.19 would have a corrected grade of 9 - 8.19 = +0.81. This corrects for differences in course means between years and between departments Prediction of Organic Chemistry Grade The correlation coefficients for organic chemistry and other variables are listed in Table 1. (The reader should remember that i i r l y is the wrrelation coefficirnt relating variables 1 and 2. then r 2 reoresents the fraction of variahle 2 oredicted h~ v&iablel.) The correlation coefficients are listed separatelv for those who took organic in their sophomore year and those who took it in their iunior year. There is a significant correlation ( P 5 0.001) between oiganic chemistry Gade and freshman grade, which does not change much whether the student takes organic in the sophomore or junior year. There is also a significant correlation between the SAT scores and organic chemistry @ 5 0.01). Table 1. Correlatlons of SAT, Freshman Grade and Organic Grade
Total (2 semesters)organic grades organic taken in: fall saph. yr. spring soph. yr. fall junior yr. spring junior yr.
Freshman Chemistv Grade Fall Spring
Malt
Verbal
SAT
SAT
0.40b
0.3Eb
0.67b
0.63b
117
0.24 0.25 0.51a 0.30
0.3Z0 0.13 0.44a 0.29
0.55' 0.5Eb 0.71b 0.71b
O.6Zb 0.53b 0.61b 0.6Zb
67 54
N*
48 46
me value of N fw mtal agylh gade 1% #errhan twice me s m ot mesemesterN valm because not all audema mrnpleted both remesten. bslgnlfioantatp s 01. a
Table 2. SAT, Freshman Grade Correlatlons
Vtnbal SAT Math SAT N
Fall Term Freshman Gmde
Spring Term Freshman Grade
0.24' 0.508 242
0.17b 0.44* 210
Significant atthe p < 0.001 level. < 0.025 level.
a Significant at lhe p
Table 3. Grade Change from Freshman to Organic Chemistry Qade Change (in grade steps)'
Number of
Students
Percentage of Sample
+1
Total A gr&
step is defined as a full letter grade (B to A) in Mis table.
One interesting feature is that the correlation coefficients with mathand verhal SAl'du not appear to Itr very different. It is important to deride whrthcr this apparent similarity is only an artifact of mmpliny. This q~~c,stion can be srttled in a scientific way by the use of an unusual statistical trst, thr Williams testi. which is descrihed in derail in the Aooendix. ~ r o &this test we can conclude there is no statistically significant difference between the correlation coefficients (and predictive power) of math and verbal SAT with overall organic chemistry grade. The freshman chemistry grade is also correlated (p < 0.001) with both the math and verbal SAT, as shown in Table 2. This is not surprising in the light of previous studies.2~Howeve1, the Williams test shows that freshman chemistry is significantly more correlated (p 5 0.001) with the math SAT, a result suspected, but not rigorously proven, in previous work. However, there is no significant difference between the correlation of math SAT and organic and verbal SAT and organic. Thus there is a striking difference in mental abilities required for the two courses. The second major conclusion is that, according to the Williams test, freshman chemistry grade is a significantly better
' Author to whom correspondence should be addressed.
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Pickering, M., J. CHEM. Eouc., 52, 512 (1975). 30zsogomonyan. A,, and Luitus. D., J. CHEM.EOUC.. 56, 173 (1979).
'Andrews, M. H., and Andrews, L., J. CmM. Eouc., 56, 231 (1979). 5Dunn, 0.J., and Clark, V., J. Amer. Stat. Assoc., 66, 904 (1971). Volume 62 Number 4
April 1985
313
Table 4.
Correlationstor Physics, Biology, Overall Science GPAs with Freshman Chemistrv
Table 6. Fate of Students Correlated with Freshman Grade
Freshman Chemistry N Math Verbal Grade SAT SAT Fall Sorim Fali Sorino .rr........-
Biology GPA Physics GPA
~
~~~
0.56 0.62
~
Freshman Grades
0.41
5 6 70
F
0.51 0.70
0.60 0.66
172
108
D C B A
103 103
-
nredictor ( o < 0.001) of oreanic chemistrv than either math br verbal SAT. To make this result more meanineful. - . Tahle 3 tabulates the relative grade change between freshman and organic chemistrv. Between freshman and oreanic chemistrv about 54% of the-sample change no more th& one-third oi'a grade step. That is, if a student gets a B- in freshman chemistry, there is a strong probability of a C+, B-, or B in organic chemistry. It is noteworthy that major changes are generally in the downward direction, that is, about 1 in 10 students stumble badly in organic chemistry, and only 8 percent improve more than one third of a grade step. Prediction of Biology, Physics, and Overall Science GPA Tahle 4 shows the correlation of physics, biology, and overall science GPA with freshman chemistry. We define overall science GPA to include organic chemistry and introductory physics and hiology courses. All the correlations are significant a t the p 5 0.001 level. Freshman chemistrv is not sienificantlv hetter than math SAT at predicting physics and biology. However it is better than verhal SAT at oredictina ~hvsicsand total science CI'A s and better than (p 5 0.001 according to the ~ i l l i a m test), math SAT a t nredictine overall science GPA (D I0.05 according to the~i1liams"test). If we divide the erouD into those who take a t least one science course beyor& frrshman chemistry, and those who do not, we find that the mean math SKI' is 632 in both cases. However, there is a striking difference between the mean uncorrected fall-term freshman grades (8.71 versus 7.50, t = 3 . 4 5 , ~5 .001), which is significant. Thus students are intuitively using their score in freshman chemistry as a predictor in the decision as to whether to continue in science or not. Prediction of Entrance into Medical School The correlations between freshman chemistry and the various MCAT sections are shown in Table 5, together with similar correlation coefficients for organic chemistry. Both freshman and organic chemistry are significantly ( p 5.005) correlated with all the science suhtests and with the MCAT science nroblems subtest Freshman chemistrv does not have CAT quite ashigh a correlation coefficient with ~ O ~ ~ ~ Mscience score as organic, hut the difference is not significant according t o the Williams test. The correlations between the MCAT reading suhtest and freshman chemistry are not significant (not surprising in view of the lack of correlation with verbal SAT). The fate of students scoring various grades in freshman chemistry in terms of medical school admission is shown in
Success rate(%)8
Fall term
~
0.39
Number of Students Did not Accepted apply1 in medical Did Not take MCAT rejected school
63 26
0 0 7 7 5
0 0 8 26 22
0 1 6
0 2
6 1
26
Spring Term F D C B A
6 14 54 44 20
5 23
-
53 79 81
33 45 77 96
'Defined as N asceptedlN taklng MCAT.
Table 6. ks grade declines, admission percentage declines, but the fraction trvine for admission declines even more. Thus freshman chemistiy is a very effective winnower, comparable to the much-feared organic. It is also clear that when students give up after finishing freshman chemistry, they are usually making the most rational decision in the light of available data. Nobody ever cites SAT scores as a reason for giving up; somehow students know intuitively that their performance in freshman chemistry is a more valid predictor of their future success in science courses. Such studies as this are intended more to help us understand the interplay of mental ahilities, motivation, and background required by the various disciplines than to help with advising. The numerical results in this paper apply strictly only a t Columbia, hut the trends and correlations are probablv of wider sienificance. However. the accurate nrediction i f students' performance from readily available i a t a remains a useful .. eoal.. as i t would heln with the tareetine .. ,. of scarce tutoring ~PSOII~CPS. Also there would he an en(mnous reduction of student anxictv and heartache if such nredictions could be made accurately. Acknowledgment This study would have not have been possible without the generous help of Patricia Geisler and the Columbia College Dean's Office. Appendix The Williams test is used to decide as to whether two correlation eaefficientscomputed from data on a single sample are indeed statistically significantlydifferent.The null hypothesisfor the test is tbat the differencein observed correlation coefficientsis due to sampling; the alternative is that the correlation coefficients are really different. In this discussion, the estimated correlation coefficientof measurement l and measurement 2 will he designated 712,that of measurement 2 with measurement 3 designated rza, and that of measurements 1 and 3 designated r l s
Table 5. Correlation with MCAT scores MCAT Section
Freshman Chem. Fall term Freshman Chem. Spring term Organic Chemishy 314
Biobgy
Chemistry
Physics
0.57 0.38 0.57
0.59
0.58 0.68
0.54 0.56
Journal of Chemical Education
0.53
Science Problems 0.60 0.48 0.66
Total Science
Total
Parts
Reading
Quantitative
MCAT
0.60 0.53
0.17 0.20
0.70
0.16
0.32 0.34 0.23
0.58 0.50 0.61
We then define a determinant
and then compute the value of
t = (7x2
- r d ( n - 3)(1 + r23)/2D3I1R/
The resulting t statistic is compared with the 1 - a12 point of the student t distribution with n - 3 degrees of freedom. Critical values for this test are widely tabulated. For detailed proofs, the reader is referred to the reference given in footnote 5.
Volume 62
Number 4
April 1985
315
