Experiment

An experiment is a systematic procedure that tests a hypothesis or explores a question by manipulating conditions and observing outcomes. Its design links controlled changes to measured results.

Independent variable: A factor deliberately changed in a study to test its effect on an outcome. It is the condition an experimenter manipulates.
Scientific method: A broad approach to inquiry that uses observation, testable explanations, and evidence to develop knowledge. Experiments are one way this wider approach tests explanations.
Observational study: A study that records conditions and outcomes without assigning an intervention or manipulating exposures. Unlike an experiment, it does not deliberately set the condition being studied.
Randomized controlled trial: A clinical study that randomly assigns participants to an intervention or comparison condition. It applies random assignment and controls to estimate treatment effects.
Reproducibility: The ability to obtain consistent results when a study is repeated using the same data, methods, and analysis. Repeated experiments can reveal whether a reported result is stable.
Dependent variable: A measured outcome that may change in response to another variable. Its observed values show whether the manipulation had an effect.
Hypothesis: A proposed explanation or prediction that can be assessed with evidence. An experiment can be designed to test its predictions.
Natural experiment: A study exploiting an external event or policy that assigns exposure in a way resembling randomization. The researcher does not directly manipulate conditions, though causal comparisons may still be possible.
Factorial experiment: An experiment that tests multiple factors and their combinations within one design. It can reveal whether one manipulated factor changes the effect of another.
External validity: The extent to which study findings apply to other populations, settings, or times. Tightly controlled conditions may limit how far experimental results generalize.

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