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Factorial Design Examples. A 2x3 Example. Study of the effect of different treatment combinations for cocaine abuse Dependent measure is severity of illness (ranges from 1 to 10) rated by treatment staff. A 2x3 Example. Factor 1: Treatment Psychotherapy Behavior modification
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A 2x3 Example • Study of the effect of different treatment combinations for cocaine abuse • Dependent measure is severity of illness (ranges from 1 to 10) rated by treatment staff
A 2x3 Example • Factor 1: Treatment • Psychotherapy • Behavior modification • Factor 2: Setting • Inpatient • Day treatment • Outpatient
A 2x3 Example Setting Main Effect of Setting In Day Out 5 7 9 7 Psych Treatment 5 7 9 7 Behmod 5 7 9
A 2x3 Example Setting Main Effect of Treatment In Day Out 5 5 5 5 Psych Treatment 7 7 7 7 Behmod 6 6 6
A 2x3 Example Setting Interaction Effect In Day Out 5 6 7 6 Psych Treatment 7 6 5 6 Behmod 6 6 6
A 2x3 Example Setting Interaction Effect In Day Out 5 7 6 6 Psych Treatment 7 8 6 7 Behmod 6 7.5 6
A Three Factor Example • Add the factor of medication dosage to the previous example. • Dependent measure is also severity of illness (ranges from 1 to 10) rated by treatment staff.
A Three Factor Example • Factor 1: Dosage • 100 mg. • 300 mg. • Factor 2: Treatment • Psychotherapy • Behavior modification • Factor 3: Setting • Inpatient • Day treatment • Outpatient
A Three Factor Example Setting In Day Out 5 7 6 6 Psych 100 mg. Treatment 7 8 6 7 Behmod 6 7.5 6 Setting In Day Out 3 5 4 4 Psych 300 mg. Treatment 5 6 4 5 Behmod 4 5.5 4
A Three Factor Example • Illustrates a 2x2x3 factorial design (12 treatment groups). • For each outcome you could have a multitude of graphs. • There are three main effects -- one for each factor. • Can you tell what effects exist?
Incomplete Factorial Design • Factors and levels are not fully crossed. • You could do this for efficiency. (3+ factors means too many groups to be feasible.) • You could do this to include a single no-treatment (or placebo) control group.
Incomplete Factorial Design Setting In Day Out 5 7 6 6 Psych Treatment 7 8 6 7 Behmod 6 7.5 6 9 No-treatment control group