Psych 3 Simple Experiments

Causal Claims

Argues that a change in one
variable is responsible for
the change in another.

3 Criteria for causal claims

Covariance, temporal precedence, elimination of confounds

Variable

Something that varies of changes (variables must have 2+ levels/potential values)

Experiment

At least one variable was manipulated and at least one
variable was measured by the researcher.

Manipulated Variable

The researcher assigns participants to a particular level of the variable

Measured Variable

Research records what happens in terms of behavior of attitudes based on self-report, behavioral observations, or physiological measures.

Independent Variable

Manipulated

Dependent variable

measured outcome variable

Experimental variables

everything but the manipulated variable should be held constant

Control variable

Any variable that an experimenter holds constant

Independent variables answer what question

“compared to what” (comparison group/condition)

Covariance

how two variables change together

Temporal precedence

Cause variable PRECEDES the effect variable

Design Confound

A second variable varies systematically along w/ IV and provides alternative explanation for the results.

• If you're testing whether a new teaching method works better, but the group using the new method also gets a better teacher, then the better teacher is a design confound — you can’t tell if the improvement is from the method or the teacher.

Selection Effect

When the participants in one level of the IV are systematically different than the participants in the other level or levels of the IV.
- Avoid with random assignment!

• ex) ppl choose to join study are ppl who are motivated in the subject. Health study, gym ppl join, they are healthier because they're already active, skewing results.

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