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Experimental Research
Experimental Research
Causation
Experiments allow you to determine Cause-and-Effect relationships
2 conditions
Experimental Research
Independent Variable
Dependent Variable
Extraneous Variables
Experimental Design
“It’s a Wonderful Life” In the movie, the character sees how things
would be different if 1 thing was changed – his being born
Experimental Research – Basic Statistics
Is condition A different than condition B? Significance Test
• t-test, z-test, F-test
Ho : MA = MB H1 : MA ≠ MB
You assume there is no difference until the data tells you otherwise
Experimental Research – Basic Statistics
Statistics can be based on 1 or 2 tails
A 1-tailed test has a more specific hypothesis
Condition A Condition B Condition A Condition B
A 2-tailed test is less specific
Condition A Condition B
Makeup Example - Statistics
Conduct t-test with the following data:
• 0 2 4 3 4 2 5 4 3 3
• 1 2 0 0 3 2 3 1 2 1
• t(9) = , p =
Jell-O Diet
Jell-O Diet
Diet Plan:
Jell-O Diet
Small print
Jell-O Diet
Results:
Experimental Research
Control Group Group that does not receive the treatment
Claims Without Controls
Claim #1:
Claim #2
Control Groups
No-treatment Group
Placebo Group
Placebo Effects
Thinking that you’re in the treatment group leads to
Placebo Effects
Group 1
Group 2
Placebo Effects
Manipulation Checks
Additional measure
Assess how people perceived the manipulation used in the experiment
Can be open to participants:
Can be hidden from participants:
Artificiality
Are experiments too artificial?
Artificiality – Cookie Study
Artificiality – Cookie Study
Artificiality – The College Sophomore Problem
The grand majority of psychological experiments
Artificiality – The College Sophomore Problem
Many studies are concerned with basic mammalian abilities
Researchers at different universities replicate each other’s results
Artificiality
Most studies are applicable to the real world
Example:
Simulation
Creating a realistic situation for the experiment
Simulation
Most famous simulation is probably the
Field Study
Observe experiments
Variables can be
Researcher can wait for
(Baseball) Field Study
Quasi-experimental Design
Quasi-experiments
These studies might look like experiments, but they lack the control needed to be a true experiment.
Recommended only when
Quasi-experimental Design
A researcher is interested in
A)
B)
Quasi-experimental Design
Quasi-experimental Design
Compare behavior / responses for Condition A Condition B
Analyze results in
Quasi-experimental Design
Are there age differences in terms of
Do people of different ages
Quasi-experimental Design
Example:
Quasi-experimental Design
Collect data from the following groups: 10 year olds 15 year olds 20 year olds 25 year olds 30 year olds
Quasi-experimental Design
Quasi-experimental Design
In this example… Independent variable:
Dependent variable:
Quasi-experimental Design
People cannot be randomly
However, try to obtain a
Quasi-experimental Design
Cross-sectional design Examine age differences
Cross sectional design
Quasi-experimental Design
Cross-sectional design Pros
Cons
Quasi-experimental Design
Alternative Design Longitudinal design
Quasi-experimental Design
Longitudinal design Pros
Cons
Longitudinal design