- An example
Independent variable (IV) are those that are manipulated by the experiment in a research. It is also known as predictor variable. The manupulation of IV causes an effect on the dependent variable.
Dependent variable (DV) are those that are not under the experiment’s control – the data. It is also known as criterion variable. DV is measured, predicted, or otherwise monitored and is expected to be affected by manipulation of an IV.
For example, in a research study on the relationship between frequency of advertising and sales revenue, the number of frequencies would be an IV. Sales revenue is a DV because it depends on the frequencies of advertising that do to induce buying from consumers (Effect).
The independent variable’s relationship with the dependent variable may change under different conditions. That condition is the moderator variable(MV). For example, frequency of advertising and sales revenue may be influenced by media chosen. “Media”, in this case, is a MV.
Obviously, “media” can also be a independent variable that affects the output of sales revenue and, in this case, frequency of advertising to be taken as MV.
Of course, there could be many other MVs such as “product items advertised”, “time advertised”, or “size of advertisement” that may cause an effect to DV.
In each relationship, there is at least one IV and a DV for simple relationship, all other variables are considered extraneous and are ignored.
An almost infinite number of EVs exist that might conceivably affect a given relationship. Some can be treated as IVs or MVs, but most must be either assumed or excluded from the study. EVs have little or no effect on a given situation. Most can be safely ignored. Some are important, but their impact occurs in a random fashion as to have little effect. E.g. Rainy day, GST increase, or other similar events and conditions that would have little effect on sales revenue generated by advertising although we have no control over these events.
EVs that can be conrolled, in our case, would be time to advertise, products to advertise and etc.
Intervening variable(IVV) is the factor that theoritically affects the observed phenomenon but cannot be seen, measure and manipulated. Its effect must be inferred from the effects of the IV and MV on the observed phenomenon.
E.g. In the above case, sales revenue(DV) increases as a result of a high frequency of advertising (IV) on TV(MV) at prime time (EV-control) generating a high level of brand awareness (IVV).