Experiment

experimentalexperimentationexperimentsexperimental scienceexperimental methodscientific experimentexperimental researchexperimental groupstudytesting
An experiment is a procedure carried out to support, refute, or validate a hypothesis.wikipedia
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Natural science

natural sciencesnaturalnatural scientist
Uses of experiments vary considerably between the natural and human sciences.
Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on empirical evidence from observation and experimentation.

Scientific control

controlcontrolscontrolled
Experiments typically include controls, which are designed to minimize the effects of variables other than the single independent variable. Confounding is commonly eliminated through scientific controls and/or, in randomized experiments, through random assignment.
A scientific control is an experiment or observation designed to minimize the effects of variables other than the independent variable.

Scientific method

scientific researchscientificmethod
Scientific controls are a part of the scientific method. In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses.
It involves formulating hypotheses, via induction, based on such observations; experimental and measurement-based testing of deductions drawn from the hypotheses; and refinement (or elimination) of the hypotheses based on the experimental findings.

Scientific theory

theoryscientific theoriestheories
Researchers also use experimentation to test existing theories or new hypotheses to support or disprove them.
Where possible, theories are tested under controlled conditions in an experiment.

Natural experiment

natural experimentsnaturalexperimental variable
There also exists natural experimental studies.
Natural experiments are employed as study designs when controlled experimentation is extremely difficult to implement or unethical, such as in several research areas addressed by epidemiology (like evaluating the health impact of varying degrees of exposure to ionizing radiation in people living near Hiroshima at the time of the atomic blast ) and economics (like estimating the economic return on amount of schooling in US adults ).

Causality

causalcause and effectcausation
Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated.
In general this leaves a set of possible causal relations, which should then be tested by analyzing time series data or, preferably, designing appropriately controlled experiments.

Random assignment

randomly assignedrandomizationassignment of treatments to units
Confounding is commonly eliminated through scientific controls and/or, in randomized experiments, through random assignment.
Random assignment or random placement is an experimental technique for assigning human participants or animal subjects to different groups in an experiment (e.g., a treatment group versus a control group) using randomization, such as by a chance procedure (e.g., flipping a coin) or a random number generator.

Randomized experiment

randomized trialrandomizationrandomized
Confounding is commonly eliminated through scientific controls and/or, in randomized experiments, through random assignment.
In science, randomized experiments are the experiments that allow the greatest reliability and validity of statistical estimates of treatment effects.

Clinical trial

clinical trialsclinical studiesclinical study
When used, however, experiments typically follow the form of the clinical trial, where experimental units (usually individual human beings) are randomly assigned to a treatment or control condition where one or more outcomes are assessed.
Clinical trials are experiments or observations done in clinical research.

Social science

social sciencessocial scientistsocial
Uses of experiments vary considerably between the natural and human sciences.
The social sciences developed from the sciences (experimental and applied), or the systematic knowledge-bases or prescriptive practices, relating to the social improvement of a group of interacting entities.

Experimental economics

experimental economistexperimentseconomic experiments
For example, agricultural research frequently uses randomized experiments (e.g., to test the comparative effectiveness of different fertilizers), while experimental economics often involves experimental tests of theorized human behaviors without relying on random assignment of individuals to treatment and control conditions.
Experimental economics is the application of experimental methods to study economic questions.

Empirical research

empiricalempirical studiesempirical method
In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses.
These predictions can then be tested with a suitable experiment.

Scientific modelling

modelmodelingmodels
In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses.
Such a simulation can be useful for testing, analysis, or training in those cases where real-world systems or concepts can be represented by models.

Hypothesis

hypotheseshypotheticalhypothesized
In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses. An experiment is a procedure carried out to support, refute, or validate a hypothesis.
The formulated hypothesis is then evaluated where either the hypothesis is proven to be "true" or "false" through a verifiability- or falsifiability-oriented experiment.

Laboratory

laboratorieslaboratory equipmentlab
Because of the importance of controlling potentially confounding variables, the use of well-designed laboratory experiments is preferred when possible.
A laboratory (, ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed.

Confounding

confounding factorconfounding variableconfounding variables
An experiment must also control the possible confounding factors—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results.
For these reasons, experiments offer a way to avoid most forms of confounding.

Psychology

psychologicalpsychologistpsychologists
In some disciplines (e.g., psychology or political science), a 'true experiment' is a method of social research in which there are two kinds of variables.
Also since James defined it, the term more strongly connotes techniques of scientific experimentation.

Scientist

scientistsresearch scientistscience
Francis Bacon (1561–1626), an English philosopher and scientist active in the 17th century, became an influential supporter of experimental science in the English renaissance.
Scientists include experimentalists who mainly perform experiments to test hypotheses, and theoreticians who mainly develop models to explain existing data and predict new results.

Average treatment effect

treatment effectsaverage treatment effect (ATE)average effect
In contrast to norms in the physical sciences, the focus is typically on the average treatment effect (the difference in outcomes between the treatment and control groups) or another test statistic produced by the experiment. In the design of experiments, two or more "treatments" are applied to estimate the difference between the mean responses for the treatments.
While an experiment ensures, in expectation, that potential outcomes (and all covariates) are equivalently distributed in the treatment and control groups, this is not the case in an observational study.

Statistics

statisticalstatistical analysisstatistician
This equivalency is determined by statistical methods that take into account the amount of variation between individuals and the number of individuals in each group.
An experimental study involves taking measurements of the system under study, manipulating the system, and then taking additional measurements using the same procedure to determine if the manipulation has modified the values of the measurements.

Blinded experiment

double-blinddouble blindblinded
Such experiments are generally double blind, meaning that neither the volunteer nor the researcher knows which individuals are in the control group or the experimental group until after all of the data have been collected.
In a blind or blinded experiment, information which may influence the participants of the experiment is withheld (masked or blinded) until after the experiment is complete.

Replication (statistics)

replicationreplicatereplicates
Typically, experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication.
In engineering, science, and statistics, replication is the repetition of an experimental condition so that the variability associated with the phenomenon can be estimated.

Design of experiments

experimental designdesignExperimental techniques
In the design of experiments, two or more "treatments" are applied to estimate the difference between the mean responses for the treatments.
The term is generally associated with experiments in which the design introduces conditions that directly affect the variation, but may also refer to the design of quasi-experiments, in which natural conditions that influence the variation are selected for observation.

Spillover (experiment)

estimate spillover effects
Experiments can be also designed to estimate spillover effects onto nearby untreated units.
In experiments, a spillover is an indirect effect on a subject not directly treated by the experiment.

Political science

political scientistPolitical Sciencespolitical analyst
In some disciplines (e.g., psychology or political science), a 'true experiment' is a method of social research in which there are two kinds of variables.
Because political science is essentially a study of human behaviour, in all aspects of politics, observations in controlled environments are often challenging to reproduce or duplicate, though experimental methods are increasingly common (see experimental political science).