Assignment
1. Subjects were randomly assigned to one of four groups in an exploratory study of the
effect of different drugs on motion sickness. The data provided below were subjected to
an analysis of variance, resulting in FOBT = 10.0.
n1 = 8 n2 = 7 n3 = 10 n4 = 7
x1 = 12.0 x2 = 6.5 x3 = 13.1 x4 = 8.5
First, determine whether the ANOVA is significant (with α ≤ .01), and, if so, determine
whether there is a significant difference between the mean scores of groups 2 and 3, 2
and 4, and 2 and 1, using the post hoc procedure that allows you to use α ≤ .01 for each
comparison.
2. Subjects were randomly assigned to one of four treatment conditions. After treatment, the
following data were obtained:
n1 = 8 n2 = 10 n3 = 7 n4 = 9
x1 = 6.5 x2 = 5.5 x3 = 8.75 x4 = 12.0
In addition, the standard deviation of the scores of all 34 subjects was 3.50.
a) Before the experiment, the researcher predicted that group 3 would obtain a
significantly higher mean than group 2, and that there would be no significant difference
between the means of groups 1 and 2. Perform the appropriate test(s) to determine
whether these predictions were borne out. (α ≤ .05)
b) After the data had been collected, the researcher wished to determine whether there
was a significant difference between x4 and x1, and between x3 and x1. Using α ≤ .05,
perform the necessary test(s) and, when comparing these means, use whichever valid
procedure gives you the smallest critical value.
3. A researcher begins with a sample of 60 subjects and randomly assigns 12 to each of 5
treatment conditions. Based on his reading of other studies in the area, the researcher
predicts that group 3 will obtain a significantly different mean from group 1, and that
group 4 will obtain a significantly higher mean than group 1.
a) Given the following data (note that some subjects have dropped out) are the
researcher's predictions supported with α ≤ .01?
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