introduction to psychology methods: experiments, surveys and correlations prof. jan lauwereyns...

Introduction to Psychology

Methods: Experiments,Surveys and correlations

Prof. Jan Lauwereyns

jan@sls.kyushu-u.ac.jp

http://www.sls.kyushu-u.ac.jp/~dubito/links

Look under “Classes”

Check “Psychology”

• Research Question:Research Question: Will participants be more altruistic if they see a video depicting human suffering?

• Research Question:Research Question: Will participants be more altruistic if they see a video depicting human suffering?

• Method:

Research Participants

Video Amount Donated

IV: Video of starving children in Africa. DV: Amount of money donated by subjects to UNICEF.

$3.64$3.64

• Research Question:Research Question: Will participants be more altruistic if they see a video depicting human suffering?

• Method:

Research Participants

Video Amount Donated

IV: Video of starving children in Africa. DV: Amount of money donated by subjects to UNICEF.

$3.64$3.64

PROBLEM:PROBLEM: Is $3.64 high, low, or medium?

Would it help to add a pretest?

• Allows us to statistically compare pre and post scores• If donation goes from low to high than we may

conclude that our experiment worked• There are some potential problems with this design

Pretest

($ donated)

Video Post-test

($ donated)

Research Participants

One group pretest/post-test designOne group pretest/post-test design

$3.64$3.64$2.85$2.85

TestingTestingTestingTesting

Taking the pretest may change the participant’s responses on the post-test.

How to Avoid• Determine whether a pretest is necessary• Disguise your pretest

Some problems are hard to avoid,but can be taken into account:

Comparing an experimental condition against a control condition

But watch out for those confounding factors…

Research Participants

Video Amount Donated

Research Participants

Control Group (neutral video)

Amount Donated

PsychologyPsychology

MarketingMarketing $2.45$2.45

$4.82$4.82Experimental group:

Control group:

A new problem

SelectionSelectionSelectionSelection

Participants who form the two groups in the experiment are chosen from existing natural groups

How to Avoid• Randomly assign participants to conditions • If not possible, try to get equivalent groups

Anatomy of a Good Experiment: Effects of Video on AltruismRepresentative Sample

Random Assignment

Experimental Group Control Group

Persuasive video Neutral video

Behavior ($ donated) Behavior ($ donated)

Operational Definition of Altruism= $ donated to UNICEF

Experimental

Control

20 2010 10

1 1015 520 10

100 580 1520 2020 1010 5

29.60 11.0032.77 5.68

Standard deviation

Average

Not significant

Experimental

Control

Experimental

Control

20 20 20 2010 10 20 10

1 10 11 1015 5 25 520 10 20 10

100 5 60 580 15 80 1520 20 20 2020 10 20 1010 5 20 5

29.60 11.00 29.60 11.0032.77 5.68 22.07 5.68

-40

+10

Experimental

Control

Experimental

Control

20 20 20 2010 10 20 10

1 10 11 1015 5 25 520 10 20 10

100 5 60 580 15 80 1520 20 20 2020 10 20 1010 5 20 5

29.60 11.00 29.60 11.0032.77 5.68 22.07 5.68

-40

+10

Experimental

Control

Experimental

Control

20 20 20 2010 10 20 10

1 10 11 1015 5 25 520 10 20 10

100 5 60 580 15 80 1520 20 20 2020 10 20 1010 5 20 5

29.60 11.00 29.60 11.0032.77 5.68 22.07 5.68

-40

+10

Smaller standard deviation

Significant

Not significant

Size Weight

176 81163 57159 52189 84172 89191 81167 67182 78171 60163 66

173.3 71.511.08603 12.7301

Size Weight

176 81163 57159 52189 84172 89191 81167 67182 78171 60163 66

173.3 71.511.08603 12.7301

Positive correlation:

More of one thing,corresponds with more of

another thing

Positive correlation:

More of one thing,corresponds with more of

another thing

More speed, more accidents

Negative correlation:

More of one thing,corresponds with less of

another thing

Negative correlation:

More of one thing,corresponds with less of

another thing

More training, less accidents

No correlation:

More of one thing,does not correspond with more

or lessof another thing

e.g., Survey about driving behavior

Ask about…-age, experience-how often drive, what kind of car…-where, how fast…-past accidents, traffic violations…

Try to establish correlations

e.g., Survey about driving behavior

Ask about…-age, experience-how often drive, what kind of car…-where, how fast…-past accidents, traffic violations…

Try to establish correlations

[ Can be inspiration for new experiments ]