Research Methods Complex Designs

Lecture Outline One-way Designs Factorial Designs Main effects Interactions

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

Foot-in-the-Door Compliance with Large Request

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

A) Lack of Precise Information Motivation and performance on a motor task 2 levels of reward $0 $4 AMOUNT OF REWARD PERFORMANCE 100 90 80 70 50 60

A) Lack of Precise Information Increased to five levels Positive monotonic relationship $1 $2 $3 $0 $4 AMOUNT OF REWARD PERFORMANCE 100 90 80 70 50 60

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 . Level 1 Level 2 Level 3 Low High DEPENDENT VARIABLE

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

Increasing the IVs: 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 Number of levels of first IV of second IV of third IV X

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

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

Main Effects Effect each variable has by itself DV: Willingness to accept increases in tuition Persuasive Argument Head Movement Decrease Increase Nodding 400 630 Shaking 485 465

Main Effect for Head Movement Persuasive Argument Head Movement Increase Decrease Overall means Nodding 400 630 515 Shaking 485 465 475

Main Effect for Type of Argument Persuasive Argument Head Movement Increase Decrease Nodding 400 630 Shaking 485 465 Overall means 442.5 547.5

Both Main Effects Persuasive Argument Head Movement Increase Decrease Overall means Nodding 400 630 515 Shaking 485 465 475 442.5 547.5

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 Let’s take a closer look

Interactions Persuasive Argument We can look at the data to detect the interaction YUCK!! Persuasive Argument Head Movement Decrease Increase Nodding 400 630 Shaking 485 465

Interactions We can look at a line graph 

Interactions Or we can look at a bar graph 

Concept Check A professor randomly assigns students to one of four conditions: Learn words in the morning and drink 2 cups of coffee Learn words in the afternoon and drink 2 cups of coffee Learn words in the morning and drink no coffee Learn words in the afternoon and drink no coffee What are the main effects and the interactions in this design? What questions would you ask to evaluate these effects?

Concept Check Main effect 1: Coffee factor Are there any differences in students who received coffee compared to those who didn’t? 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.

Main Effects & Interactions No main effect of A or B, no interaction Violent TV Threat A1 A2 B1 20 B2 Provocations -

Main effect of A, no main effect of B and no interaction Violent TV Threat A1 A2 B1 20 40 30 B2 Provocations -

Main effect of B, no main effect of A and no interaction Violent TV Threat A1 A2 B1 20 B2 40 30 Provocations -

Main effect of A and B, no interaction Violent TV Threat A1 A2 B1 20 10 B2 40 30 Provocations -

No main effect of A or B; interaction Violent TV Threat A1 A2 B1 40 20 30 B2 Provocations -

Main effect of A, no main effect of B; interaction Violent TV Threat A1 A2 B1 40 20 B2 30 10 Provocations

Main effect of B, no main effect of A; interaction Violent TV Threat A1 A2 B1 20 10 B2 40 30 Provocations

Main effect of A and B; interaction Violent TV Threat A1 A2 B1 20 B2 40 30 Provocations -

Hands on Activities Design Identification Outcomes of Factorial Designs