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CHAPTER 10

COMPLEX EXPERIMENTAL

DESIGNS

Dr. Rodica Ghinescu

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INCREASING THE NUMBER OF

LEVELS OF AN INDEPENDENT

VARIABLE

Provides more information about the

relationship than a two level designComparing Two or More Groups

I.E. How dogs, cats, and birds as opposed

to dogs alone have beneficial effects on

nursing home residents

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

Factorial Designs: Designs with more

than one independent variable (orfactor)

Simplest Factorial Design

2 x 2 factorial designHas two independent variables

No of levels of first IV x no levels of second

IV x No of levels of 3rd variable

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Examples of factorial designs

2 x 3 (two by three design) has two

independent variables; the first

independent variable has 2 levels; the

second independent variable has 3 levels

Can easily determine the number of

conditions in the experiment by multiplying

the number of levels in each factor

6conditions here

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2 x 2 factorial design

Gender (IV B) Obesity(IV A)

obese not obese

Overall means

(main effect of B)

Woman 13 41 27.0

Man 13 18 15.5

Overall means (maineffect of A)

13 29.5

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

Interpretation of Factorial Designs

Main effects of an independent variable arethe effects of each independent variable

while controlling for the effects of the other

independent variable(s)

Interaction between the independentvariables occurs when the influence of one

independent variable is different at different

levels of the other independent variable.

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

Interactions and Moderator Variables

Outcomes of a 2 x 2 Factorial Design1. There may or may not be a significant main effect for

independent variable A

2. There may or may not be a significant main effect forindependent variable B

3. There may or may not be a significant interaction between

the independent variables(See results in next five slides)

Interactions and Simple Main Effects Simple main effect of type of questioner

Simple main effect of type of question

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INCREASING THE NUMBER OF

VARIABLES: FACTORIAL

DESIGNS

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

Assignment Procedures and Factorial

Designs Independent groups design

Repeated measures design

Mixed factorial design using combinedassignment

C S G O

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

INCREASING THE NUMBER OF

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS

INCREASING THE NUMBER OF

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INCREASING THE NUMBER OF

INDEPENDENT VARIABLES:

FACTORIAL DESIGNS