Psychology Research Methods: Variables, Sampling, Ethics & Design

Hypothesis

A testable prediction.

Falsifiable

Evidence could show the prediction is wrong.

Operational definition

The exact measurable/observable way a variable is defined.

Independent variable (IV)

What the researcher manipulates.

Dependent variable (DV)

The outcome the researcher measures.

Confounding variable

Another factor that changes with the IV and could explain the results.

Experimental group

Receives the treatment/condition.

Control group

Comparison group.

Random assignment

Places participants into groups by chance; helps reduce confounding variables.

Placebo

Inactive treatment.

Placebo effect

Change caused by expectations rather than the treatment itself.

Single-blind

Participants do not know their condition.

Double-blind

Participants and researchers interacting with them do not know the condition; helps reduce experimenter bias.

Quantitative data

Numerical data - scores, counts, ratings.

Qualitative data

Descriptive data - interviews or open-ended responses.

Likert-style item

Asks for a degree of agreement/rating.

Structured interview

Predetermined questions asked consistently.

Survey

Self-report of attitudes/behaviors.

Self-report bias

Inaccurate reporting.

Social desirability bias

Answering in a way that looks socially acceptable.

Population

Entire group of interest.

Sample

Participants actually studied.

Representative sample

Reflects important characteristics of the population.

Random sampling

Members of the population have an equal chance of selection.

Convenience sampling

Selecting people because they are easy to access.

Sampling bias

The selection method favors some members of the population.

Generalizability

How well findings from a sample can apply to the larger population.

IRB

Reviews proposed research to help protect human participants.

Informed consent

An informed adult voluntarily agrees to participate.

Informed assent

A minor agrees after an age-appropriate explanation; parent/guardian permission may also be required.

Protection from harm/nonmaleficence

Protect participants from unnecessary physical and psychological harm.

Confidentiality

Identity may be known, but information is protected.

Anonymity

Identity is not linked to responses.

Deception

Information may be withheld/misrepresented when ethically justified.

Debriefing

The true purpose/deception is explained afterward.

Peer review

Experts evaluate research before publication.

Replication

Repeating a study to see whether similar results occur again.