Psychology Research Methods: Key Concepts and Validity Types

Basic research

Research designed to understand behavior without solving an immediate problem

Applied research

Research conducted to solve real-world problems

Empiricism

The belief that knowledge is gained through observation and measurement

Scientist-practitioner model

Clinical psychologists apply science and apply treatment

Scientific theory

An organized explanation of observed behavior

Hypothesis

A testable prediction derived from theory

Data

Information collected through systematic observation or measurement

Theory-data cycle

Theory leads to hypothesis, hypothesis leads to data, data refine theory

Comparison group

A group that does not receive treatment and serves as a baseline

Control group

A group with no manipulation

Experimental group

Group exposed to the independent variable

Probabilistic reasoning

Understanding that results indicate likelihood, not certainty

Generalization

Applying results beyond the sample

Confirmation bias

Seeking information that supports existing beliefs

Belief perseverance

Holding onto beliefs despite contradictory evidence

Availability heuristic

Judging likelihood based on how easily examples come to mind

Overconfidence bias

Believing you are more accurate than you actually are

Hindsight bias

Seeing outcomes as obvious after they occur

Independent variable (IV)

Variable manipulated by researcher

Dependent variable (DV)

Variable measured in study

Manipulated variable

A variable controlled by researcher

Measured variable

A variable observed or recorded

Frequency claim

Describes how common something is

Association claim

Shows that two variables are related

Causal claim

Shows one variable causes another

Construct validity

Measures what it claims to measure

Internal validity

Cause-and-effect confidence

External validity

Generalizability

Statistical validity

Whether result is statistically believable

Reliability

Consistency of measurement

Validity

Accuracy of measurement

Test-retest reliability

Consistency over time

Interrater reliability

Consistency across observers

Internal consistency

Consistency across test items

Face validity

Appears valid

Criterion validity

Correlates with outcome

Convergent validity

Agreement with similar measures

Discriminant validity

Distinct from unrelated measures

Covariance

Variables change together

Temporal precedence

Cause comes before effect

Third-variable problem

An unmeasured variable explains relationship

Self-report measures

Questionnaires, surveys

Behavioral measures

Observed actions

Physiological measures

Bodily responses (heart rate, EEG, etc.)

Nominal scale

Categories only

Ordinal scale

Ordered categories

Interval scale

Equal intervals, no true zero

Ratio scale

True zero point

Population

Entire group of interest

Sample

Subset of population

Census

All members surveyed

Random sample

Every member has equal chance

Biased sample

Unrepresentative group

Self-selection bias

Participants choose themselves

Simple random sample

All equal odds

Stratified sample

Groups proportionally represented

Cluster sample

Groups randomly selected

Systematic sample

Every nth person chosen