PSY 870: Module 4 Problem Set
2 × 3 Between-Subjects Factorial ANOVA: Study
Environments by Gender
This study investigates whether study environment affects
academic performance. In addition, this study investigates whether sex of
student "moderates" the effect of study environment on academic
performance (that is, do males and females differ in how much benefit they get
from studying in certain environments).
During the first half of the spring semester, 120 male
students and 120 female students in grade 10 at a public high school in a large
metropolitan area in the southwestern region of the United States were randomly
assigned to one of three study environment: study in front of the TV, at the library,
or in the food court. The students could ONLY study in the environment to which
they were assigned during the research period. At the end of the 7-week
research period, mid-term GPA was computed for each student. A change score was
computed for each student: each student's spring midterm GPA was subtracted
from his or her GPA for the preceding fall semester. The difference was each
student's GPA Improvement score. The GPA improvement score was used to measure
Using the SPSS 2 × 3 ANOVA data file for Module 4 (located
in Topic Materials), answer the following questions.NOTE: Helpful hints are provided here for you to use while
answering these questions. There is no separate answer sheet/guide to use while
doing this assignment.
are the two independent variables in this study? What is the dependent
is a two-way between-subjects factorial ANOVA the correct statistic to use for
this research design?
you find any errors that the researcher made when setting up the SPSS data file
(Remember to check the variable view)? If so, what did you find? How did
you correct it?
Descriptive Statistics on the dependent variable data. What do the skewness and
kurtosis values tell you about whether the data satisfy the assumption of
a between-subjects factorial ANOVA on the data.
What do the results of the Levene's Test tell you about
your data? What does this mean in terms of interpreting the outcomes of the
What do the results of the Tests of Between-Subjects
Effects tell you? Was there a significant main effect of Environment on GPA
improvement? Was there a significant main effect of Sex on GPA improvement? Was
there a significant interaction effect of Environment X Sex on GPA improvement?
Report the results for each of these questions providing the actual F-value and p value using the following format: F(df1, df2) = ____, p =
.___ or if the p is shown as .000,
write it as p < .001; an example of this formatting is F(1, 400) = 15.4, p =
Use eta squared to provide effect size/proportion of variance accounted associated
with each F-value. If the F-value
for a main effect and/or for an interaction effect is statistically
significant, what is the eta squared (h2)
value associated with that outcome?
eta squared, h2; ignore
partial eta squared that SPSS can provide. You have to calculate eta
squared yourself. It is not given to you by SPSS, but you can use what SPSS
provides to calculate it. Eta squared is calculated by using the values in the
column headed "Type III Sum of Squares" from the table with the
results for Tests of Between-Subjects Effects." To compute eta squared,
which would be notated as h2,
take that source's Type III Sum of Squares and divide it by the value for
Corrected Total in the same column. For example, if the Type III Sum of Squares
for Environment had been 4.5 rather than 4.696, you would divide 4.5 by 14.677
to get the effect size for Environment. If the Type III Sum of Squares for Sex
had been 2.0, you also would divide that by 14.677, etc. Interpret these eta
squared results for effect size using the following guidelines from Cohen
.01 ~ small
.06 ~ medium
.14 ~ large
If the result for the main effect of Environment was
statistically significant, what did you find out when you performed post hoc
tests (Tukey HSD) to look at possible statistically significant differences in
the pairs of means for Environment groups?
If the result for the interaction of Environment X Sex
was statistically significant, what follow up tests did you perform to
understand what was going on here? That is, what did you do to find out what
was different for males in the various study Environments versus for females in
the various study Environments in effects on GPA improvement? What did you
When you have a factorial ANOVA and the interaction
effect is significant, does the researcher give much attention to any
significant main effects when interpreting the results of the study?
Citing the results of your statistical analyses, what
is the conclusion you can draw (and support) regarding research question that
was posed in this research (see problem statement)? Write a results section for
this study that expresses and supports this conclusion.
the sample write-up of the results for the Two-Way Between-Subjects ANOVA
example that is in the textbook to see what you should report and how to say
it. Just substitute the correct language and values for the analyses you have
done for this problem.