Quantitative methods deal with discrete and directly measurable units of data. the American Psychological Association (2009) defines quantitative psychology as:

...the study of methods and techniques for the measurement of human attributes, the statistical and mathematical modeling of psychological processes, the design of research studies, and the analysis of psychological data.

The Quantitative approach is based on testing hypotheses by conducting experiments. The research tools within the experiments are known as methods and are dictated by the particular requirements and framework of the experiment itself (the methodology). Through the employment of these various methods, researchers manipulate and measure variables in order to draw conclusions from the results they see.

Types of Variable

Within an experiment, the researcher measures variables with assessed degrees of reliability and validity. There are generally four types of variables to consider:

Independent Variable (IV)

A individual feature or aspect of an environment that is changed or manipulated in some way in order to determine any resultant effects on the...

Dependent Variable (DV)

This is the measured variable in the experiment. Ideally, the changes observed will be dependent upon the variations in the Independent Variable described above.

Extraneous Variable (EV)

Other variables which may have an effect on the outcome of the experiment. The context and environment (known as situational variables) and the participants of the experiment all contain variables which can "skew" the data collected and hence the results obtained. These must be predicted, controlled, examined and documented as far as possible.

Confounding Variables (CV)

The "fly in the ointment" of an experiment. Confounding variables could be said to cast into doubt the independence of the Independent Variable. That is to say, if researchers become aware of a Confounding Variable, they can no longer be sure that their observations of variation in the Dependent Variable are genuinely attributable to the changes they made to the Independent Variable.

The unwanted effects of Extraneous and Confounding Variables can be dealt with largely in the design and planning stages of the experiment.

So, to re-cap; an experimenter manipulates Independent Variables to observe effects on Dependent Variables whilst striving to identify and control Extraneous and Confounding Variables at every stage of the experiment.

Levels of Variable

The scope for change within variables is generally categorised into levels. The number of levels is dictated by the nature of the variable and the design of the experiment.

Lots of Variables

Of course, researchers may be interested in changing or measuring more than one thing (variable).

When designing experiments, Psychologists use a specific terminology to express the numbers and associated levels of manipulated (Independent) variables. for example:

References


Report of the Task Force for Increasing the Number of Quantitative Psychologists (2009). apa.org. Retrieved 24 October, 2017, from http://www.apa.org/research/tools/quantitative/default.aspx