An experiment is experimental because researchers actively introduce an intervention or manipulation (independent variable) and then observe its effect on an outcome (dependent variable).
Here's a breakdown of what makes an experiment "experimental":
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Manipulation of an Independent Variable: The core of an experiment is that the researcher changes something (the independent variable). This manipulation distinguishes it from observational studies, where researchers simply observe without intervening.
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Measurement of a Dependent Variable: The researcher measures the outcome or effect of the manipulation on another variable (the dependent variable).
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Control: Experiments attempt to control extraneous variables that could influence the outcome. This control helps ensure that any observed changes in the dependent variable are actually due to the manipulation of the independent variable and not something else. Common control methods include:
- Random Assignment: Participants are randomly assigned to different groups (e.g., a treatment group and a control group) to minimize pre-existing differences between the groups. This is particularly important in Randomized Controlled Trials (RCTs).
- Control Group: A group that does not receive the intervention or receives a placebo, providing a baseline for comparison.
- Standardized Procedures: Ensuring that all participants experience the experiment in the same way, except for the manipulation of the independent variable.
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Intervention: As highlighted in the provided reference, experimental studies involve the introduction of an intervention. This intervention is the application of the independent variable to one or more groups of participants.
Example:
Imagine a study examining the effect of a new drug on blood pressure.
- Independent Variable: The drug (present or absent).
- Dependent Variable: Blood pressure.
- Intervention: Administering the drug to one group (treatment group).
- Control: A control group receives a placebo. Participants are randomly assigned to either the treatment or control group. Blood pressure is measured for both groups before and after the treatment period.
In this example, the researcher is actively doing something (administering the drug) and then observing its effect. This active manipulation and measurement, coupled with attempts to control for other factors, are what make this study experimental. If the researchers were simply observing people who were already taking the drug, it would be an observational study, not an experiment.
