Education

Learn what reliability means in psychology, the four main types — test–retest, inter-rater, internal, and external — plus how psychologists test and improve consistent results.

Discover the four main types of validity in psychology — internal, external, construct, and criterion validity — with clear examples and how to improve each for valid research.

Demand characteristics occur when participants guess a study’s purpose and change their behaviour. Learn what they are, examples, and how psychologists control them.

Extraneous and confounding variables can distort results in psychological research. Learn their types, examples, and how to control them for reliable, valid experiments.

Understanding experimental designs in psychology helps researchers and students test ideas scientifically. This guide explains the four main designs — independent, repeated measures, matched pairs, and quasi — with examples, strengths, and weaknesses. Perfect for A-level revision or anyone learning how psychologists structure their experiments.