Biostatistics

568 CHAPTER 11 REGRESSION ANALYSIS: SOME ADDITIONAL TECHNIQUES
11.3.3 One purpose of a study by Connor et al. (A-8) was to examine reactive aggression among
children and adolescents referred to a residential treatment center. The researchers used the
Proactive/Reactive Rating Scale, obtained by presenting three statements to clinicians who
examined the subjects. The respondents answered, using a scale from 1 to 5, with 5 indicating
that the statement almost always applied to the child. An example of a reactive aggression
statement is, “When this child has been teased or threatened, he or she gets angry easily and strikes
back.” The reactive score was the average response to three statements of this type. With this
variable as the outcome variable, researchers also examined the following: AGE (years),
VERBALIQ (verbal IQ), STIM (stimulant use), AGEABUSE (age when first abused), CTQ
(a measure of hyperactivity in which higher scores indicate higher hyperactivity), TOTALHOS
(total hostility as measured by an evaluator, with higher numbers indicating higher hostility).
Perform stepwise regression to find the variables most useful in predicting reactive aggression in
the following sample of 68 subjects.
REACTIVE AGE VERBALIQ STIM AGEABUSE CTQ TOTALHOS
4.0 17 91 0 0 0 8
3.7 12 94 0 1 29 10
2.3 14 105 0 1 12 10
5.0 16 97 0 1 9 11
2.0 15 97 0 2 17 10
2.7 8 91 0 0 6 4
2.0 10 111 0 0 6 6
3.3 12 105 0 0 28 7
2.0 17 101 1 0 12 9
4.3 13 102 1 1 8 11
4.7 15 83 0 0 9 9
4.3 15 66 0 1 5 8
2.0 15 90 0 2 3 8
4.0 13 88 0 1 28 8
2.7 13 98 0 1 17 10
2.7 9 135 0 0 30 11
2.7 18 72 0 0 10 9
2.0 13 93 0 2 20 8
3.0 14 94 0 2 10 11
2.7 13 93 0 1 4 8
3.7 16 73 0 0 11 11
2.7 12 74 0 1 10 7
2.3 14 97 0 2 3 11
4.0 13 91 1 1 21 11
4.0 12 88 0 1 14 9
4.3 13 90 0 0 15 2
3.7 14 104 1 1 10 10
3.0 18 82 0 0 1 7
4.3 14 79 1 3 6 7
1.0 16 93 0 0 5 8
4.3 16 99 0 1 21 11
(Continued )