According to the theory of the inoculation effect, people are more resistant to changing their attitudes towards something if they have been mildly attacked for those attitudes in the past than if they have never been challenged. Suppose college students who agree with the statement "Most forms of mantel illness are not contagious" are divided into three groups. The 'support' group receives information that is mildly supportive of the statement. The 'inoculation' group receives information that is mildly critical of the attitude. The control group receives no information about the attitude. Subsequently, all subjects receive a message that vigorously attacks the belief, and they are later tested for attitude change. The results are presented below. A larger score indicates greater attitude change.

Support group Inoculation group Control group

7 1 5

5 4 7

3 3 4

6 3 5

4 2 7

7 5 8

a.Prepare the source table for above

b.Determine whether the groups are significantly different.

c.Compute the percentage of variance explained by the treatment effects (²).