Assignment 3
Chapter Exercise
10. In a study of the effects of stress on illness, a researcher tallied the number of
colds people contracted during a 6-month period as a function of the amount of
stress they reported during that same time period. There were three stress levels:
minimal, moderate, and high stress. The sums of squares appear in the following
ANOVA summary table. The mean for each condition and the number of subjects per
condition are also noted.
Source
Between groups
Within groups
Total
Stress Level
Minimal
Moderate
High
df
SS
22.167
14.750
36.917
Mean
3
4
6
MS
F
N
4
4
4
a. Complete the ANOVA summary table.
b. Is Fobt significant at α = .05; at α = .01?
c. Perform post hoc comparisons if necessary.
d. What conclusions can be drawn from the
F-ratio and the post hoc comparisons?
e. What is the effect size, and what does this mean?
f. Graph the means
12. A researcher conducted an experiment on the effects of a new “drug” on depression.
The researcher had a control group that received nothing, a placebo group and
an experimental group that received the “drug”. A depression inventory that provided a
measure of depression on a 50 point scale was used (50 indicates that an individual is
very high on the depression variable). The ANOVA summary table appears next, along
with the mean depressing score for each condition.
Source
df
Between groups
Within groups
Total
SS
1,202.313
2,118.00
3,320.313
“Drug” Condition
Control
Placebo
“Drug”
Mean
36.26
33.33
24.13
MS
F
n
15
15
15
A. Complete the ANOVA summary table
b. Is F obt significant at α = .05; at α = .01?
c. Perform post hoc comparisons if necessary
d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?
e. What is the effect size, and what does this mean?
f. Graph the means.
14) A researcher has been hired by a pizzeria to determine which type of crust customers
prefer. The restaurant offers three types of crust: hand tossed, thick, and thin.
Following are the mean number of l inch pieces of pizza eaten for each condition from 10
subjects who had the opportunity to eat as many pieces with each type of crust as
they desired. The ANOVA summary table also follows
Source
Subject
Between
Error
Total
Crust Type
Hand-tossed
Thick
Thin
df
SS
2.75
180.05
21.65
204.45
Mean
2.73
4.20
8.50
MS
F
n
10
10
10
a) Complete the ANOVA summary table.
b) Is F obt significant at α = .05; at α = .01?
c) Perform post hoc comparisons if necessary.
d) What conclusions can be drawn from the F-ratio and the post hoc comparisons?
e) What is the effect size, and what does this mean?
f) Graph the means
