Exercise 33
1. Do the data meet criteria for homogeneity of variance? Provide a rationale for your answer.
The data meet criteria for homogeneity of variance because the Test of Homogeneity of Variance
was not significant, p = 0.455
Test of Homogeneity of
Variances
HoursWorked
Levene
Statistic
df1
df2
Sig.
.840
2
12
.455
2. If calculating by hand, draw the frequency distribution of the dependent variable, hours worked
at a job. What is the shape of the distribution? If using SPSS, what is the result of the Shapiro-
Wilk test of normality for the dependent variable?

The shape of the distribution is roughly normal.
There may be a slight skew to the right.
The
Shapiro-Wilk test of normality shows that it is a normal distribution with p = 0.314.
Tests of Normality
Kolmogorov-Smirnov
a
Shapiro-Wilk
Statist
ic
df
Sig.
Statist
ic
df
Sig.
HoursWor
ked
.206
15
.085
.934
15
.314
a. Lilliefors Significance Correction
3. What are the means for three groups’ hours worked on a job?
The means for the three groups are Supported M = 14.6, TAU Observational M = 15.2, TAU
Randomized M = 26.6.
Descriptives
HoursWorked
N
Me
an
Std.
Deviat
ion
Std.
Error
95% Confidence Interval for
Mean
Minimum
Maximum
Lower
Bound
Upper Bound
Supported
5
14.
60
6.504
2.90
9
6.52
22.68
8
24
TAU
Observational
5
15.
20
3.701
1.65
5
10.60
19.80
9
18
TAU
Randomized
5
26.
60
7.436
3.32
6
17.37
35.83
15
35
Total
1
5
18.
80
8.029
2.07
3
14.35
23.25
8
35

4. What are the F value and the group and error df for this set of data?
The F = 6.162, error df = 2, and group df = 12.
ANOVA
HoursWorked
Sum of
Squares
df
Mean Square
F
Sig.
Between Groups
457.200
2
228.600
6.162
.014
Within Groups
445.200
12
37.100
Total
902.400
14
5. Is the F significant at α = 0.05? Specify how you arrived at your answer.
The F is significant at an alpha of 0.05 because the test statistic shows a p value of 0.014, well
below the alpha for type 1 error.
6. If using SPSS, what is the exact likelihood of obtaining an F value at least as extreme as or as
close to the one that was actually observed, assuming that the null hypothesis is true?
The likelihood of obtaining an F value at least as extreme is considered type 1 error and is equal
to the p value of the observed statistic, which is 1.4%
7. Which group worked the most weekly job hours post-treatment? Provide a rationale for your
answer.

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- Spring '14