Research Methods

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Research Methods

• Complex Designs

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Lecture Outline

• One-way Designs
• Factorial Designs
• Main effects
• Interactions

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One-Way Designs

• One-way refers to one independent variable
• Two groups design
• The simplest one-way design
• One IV with 2 levels
• Foot-in-the-door technique
• Get person to consent to small task first, then
  ask for larger task
• EXAMPLE Freedman Fraser (1966)
• Went door to door
• Small request Sign petition
• Large request Huge, ugly sign on lawn
• Experimental group small then large
• Control group large request only

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Foot-in-the-Door
Compliance with Large Request
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More than two levels

• Several reasons you may want more than 2 levels
  of one IV
• A) 2 levels cannot provide much information
  about the exact relationship between IV and DV
• B) 2 levels cannot detect curvilinear
  relationships
• C) May be interested in more than 2 groups

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A) Lack of Precise Information

• Motivation and performance on a motor task
• 2 levels of reward

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A) Lack of Precise Information

• Increased to five levels
• Positive monotonic relationship

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B) Curvilinear relationships

• Nonmonotonic
• Increases in the value of one variable are
  accompanied by increases and decreases in values
  of another
• Fear and attitude change
• .

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C) Interested in More Than Two Things

• Effects of animal companionship on nursing home
  residents
• 2 group design
• Dog / No Dog
• More than 2 groups
• Dog, Bird, Cat, No animal
• Stress reducing techniques (Bruning Frew, 87)
• 4 group design
• Exercise, management skills training, medication,
  control
• All 3 techniques decreased blood pressure and
  pulse

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Increasing the IVs Factorial Designs

• Factorial designs
• More than one independent variable (or factor)
• Determining the number of conditions
• 2 x 3
• 6 conditions
• 3 x 3
• 9 conditions
• 2 x 2 x 2
• 8 conditions

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A 2 x 2 Design

• Head movement and persuasive arguments
• Participants listened to a persuasive argument
  while moving their head
• Independent variables
• Persuasive argument Tuition increase or tuition
  decrease
• Head movement Nod head or shake head
• Conditions?
• 2 x 2 4

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A 2 x 2 Design
Persuasive Argument
Movement of Head
Tuition decrease
Tuition increase
Nodding
Shaking
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Main Effects

• Effect each variable has by itself
• DV Willingness to accept increases in tuition

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Main Effect for Head Movement
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Main Effect for Type of Argument
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Both Main Effects
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Interactions

• The effect of one independent variable depends on
  the level of the other
• There is an interaction in the persuasive
  argument study
• The effect of the type of argument is different
  depending on whether the person is nodding or
  shaking their head
• Lets take a closer look

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Interactions

• We can look at the data to detect the interaction
• YUCK!!

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Interactions

• We can look at a line graph ?

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Interactions

• Or we can look at a bar graph ?

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Concept Check

• Main effect 1 Coffee factor
• Are there any differences in students who
  received coffee compared to those who didnt?
• Main effect 2 Time of day factor
• Are there any differences in students who learned
  the words in the morning vs afternoon?
• Interaction Does the effect of coffee depend on
  the time of day?
• Coffee might enhance performance in the morning
  but impair performance in the afternoon.

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Main Effects Interactions
No main effect of A or B, no interaction
Provocations
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Main effect of A, no main effect of B and no
interaction
Provocations
-
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Main effect of B, no main effect of A and no
interaction
Provocations
-
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Main effect of A and B, no interaction
Provocations
-
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No main effect of A or B interaction
Provocations
-
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Main effect of A, no main effect of B interaction
Provocations
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Main effect of B, no main effect of A interaction
Provocations
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Main effect of A and B interaction
Provocations
-