An operational definition defines a psychological variable in terms of the exact procedures used to measure or observe it. Because most variables are abstract constructs that cannot be directly observed (e.g., stress), researchers must transform these conceptual definitions into concrete, quantifiable forms. For instance, stress could be operationally defined as a score on a standardized questionnaire, the concentration of cortisol in saliva, or the number of recent stressful life events experienced.

Operational Definition

The dependent variable is the numerical measure of what the outcome of the manipulation should be: the data that the experimenter gathers.

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The starting point of an experiment as a severe test is to set up a situation that tests an idea and that idea must be causal: one thing should influence another. In HCI-style experiments, this is also expressed as seeing the effect of the independent variable on the dependent variable. 


Starting point of an experiment

Dependent variable

In experimental design, an independent variable is the presumed cause within a cause-and-effect relationship. It is the specific factor that researchers actively manipulate or systematically vary to observe what change it produces in another variable.

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