Types of Experiment in Psychology: Lab, Field, Natural, Quasi
In one of psychology's best-known field experiments, 21 of 22 hospital nurses were ready to give a patient double the maximum dose of an unfamiliar dr…
Category: Articles
Peer Review in Psychology: Process, Types and Evaluation
In 1982, two psychologists resubmitted 12 already-published papers to the journals that had printed them, under made-up names. Peer review spotted onl…
Validity in Psychology: Types, Assessment and Improvement
In 1973, eight people with no mental illness claimed to hear voices and were admitted to 12 psychiatric hospitals. Not one was detected by staff, whic…
Reliability in Psychology: Types, Assessment and Improvement
When two psychiatrists independently assessed the same patients in the DSM-5 field trials, their agreement on major depressive disorder reached a kapp…
Aims and Hypotheses in Psychology: Directional vs Non-Directional
In standard psychology papers, 96% of first hypotheses are supported. In Registered Reports, where the hypothesis is fixed before any data exist, only…
Sampling Methods in Psychology: 5 Techniques With Examples
In six leading psychology journals, 96% of studies relied on samples from Western industrialised countries, which hold about 12% of the world's popula…
Experimental Design in Psychology: 3 Types With Examples
In a between-subjects experiment, one group of people judged the number 9 to be significantly larger than another group judged 221 (Birnbaum, 1999).
Spearman’s Rho: Formula, Worked Example and Table
Spearman's rho was invented by a psychologist, yet the rank formula Charles Spearman printed in 1904 is not the one students learn today. His version …
Wilcoxon Signed-Rank Test: Formula, Worked Example and Table
In 1945 the chemist Frank Wilcoxon introduced the Wilcoxon signed-rank test in a four-page paper and tried it on Darwin's maize plants. It reached the…
Mann-Whitney U Test: Formula, Worked Example and Table
The Mann-Whitney U test is often described as a test of medians, but it is not one. Two groups with identical medians can still produce a significant …