Impact of SAT scores and parttime students on university graduation
rates
A previous post
showed that SAT scores had a 25% larger impact on ontime graduation rates for
public universities than for private universities.
This post expands the model to also consider how parttime
students impact the ontime graduation rate.
Question: Add information on the percent of students
attending a university parttime to the ontime graduation rate model. Is an increase in the percent of students
attending a university parttime related to the ontime graduation rate? Does the inclusion of this information alter
the impact of SAT scores on ontime graduation rates?
Analysis: I follow the previous post and considered
different models for private and public universities. The regression coefficients for the two
models are presented below.
OnTime Graduation Rate
Model Results


Public Universities

Private Universities


Coeff.

pValue

Coeff.

pValue


SAT Measure

0.011

0

0.010

0

Part Time Student %

1.549

0.197

0.816

0.315

Constant

5.253

0

5.179

0

Sample Size

31

20


R2

86.7

84.4

Observations:
The SAT Measure remains highly significantly related to
ontime graduation rates for both private and public universities
The variable percent of students attending a university part
time is not significantly related to ontime graduation rates for either public
or private universities.
The coefficient of the SAT Measure in the public university
model is 5.7% higher than the coefficient of the SAT Measure in the private
university model. (This differential
was much larger (around 25%) when the parttime percentage variable was
excluded from the model. See previous
post on this.)
Comments:
The parttime percentage variable is
not significant but its inclusion in the model has a large impact on the
differential between the impact of SAT Scores on graduation rates in public
versus private universities.
The sample sizes (31) for public universities and (20) for
private universities are too small. To
paraphrase the movie Jaws I need a bigger boat.
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