Types of variables

There are five (5) types of variables that one is likely to find in a research study, and these are:

  1. Dependent variables
  2. Independent variables
  3. Intervening variables
  4. Extraneous variables
  5. Moderating variables

1. Independent and Dependent Variables
Independent variable is a variable that a researcher manipulates in order to determine its change or its influence on another variable (predictor variable), because it will predict the amount of variation that occurs in another variable. It is a variable which influences the dependent variable in either a positive way or a negative way.
The dependent variable attempts to indicate the total influence arising from the total effect arising from the independent variable. A dependent variable therefore varies as a function of the independent variable. In other words, it is the variable which is expected to change as a result of the presence or absence or magnitude of the independent variable. For example, does a participative leadership style (independent variable) influence job satisfaction or performance (dependent variables)? It is important to remember that there are no preordained variables waiting to be discovered ‘out there’ that are automatically assigned to one category or the other. Has Hover has noted, there is nothing very tricky about the notion of independence and dependence. But there is something tricky about the fact that the relationship of independence and dependence is a figment of the researcher’s imagination until demonstrated
convincingly. Researchers hypothesize relationships of independence and dependence: they invent them, and then they try by reality testing to see if the relationships actually work out that way.

2. Moderating Variables
In each relationship, there is at least one independent variable (IV) and a dependent variable (DV). It is normally hypothesized that in some way the IV ‘causes’ the DV to occur. For simple relationships, all other variables are considered extraneous and ignored.
In a typical office, we might be interested in a study of the effect of the four-day workweek on office productivity and hypothesize the following:

• The introduction of the six-day workweek (IV) will lead to increased office productivity perworker-hour (DV). In actual study situations, however, such a simple one-on-one relationship needs to be conditioned or revised to take other variables into account. Often one uses another type of explanatory variable of value here- the moderating variable (MV). A moderating variable is a second independent variable that is included because it is believed to have a significant contributory or contingent effect on the originally IV-DV relationship For example, one may hypothesize that
• The introduction of the six-day workweek (IV) will lead to higher productivity (DV) especially among younger workers (MV).
In this case, there is a differential pattern of relationship between the six-day week and productivity that is the result of age differences among the workers.

3. Extraneous Variables
These are those variables that affect the outcome of a research study either because the researcher is not aware of their existence, or if s/he is aware, there are not controls for them. If extraneous variables are not considered, it is difficult to determine how much influence on the dependent variable, is due to an extraneous variable and how much is due to the independent variable. Extraneous variables are sometimes referred to as confounding variables, because they confound the effect of the independent variable on the dependent variable. One might think that the kind of work being done would have an effect on any work week length impact on office productivity. This might lead to our introducing a control as follows:

• In a routine office work (EV-control), the introduction of a six-day workweek (IV) will lead to higher productivity (DV), especially among younger workers (MV). In our office example, we would attempt to control for type of work by studying the effects of the six-day week within groups performing different types of work.

4. Intervening Variables
An intervening variable is a conceptual mechanism through which the IV and the MV might affect the DV. The intervening variable (IVV) may be defined as ‘that factor which theoretically affects the observed phenomenon but cannot be seen, measured, or manipulated, its effect must be inferred from the effects of the independent and moderating variables on the observed phenomenon. In other words, it is a variable that comes between the independent and dependent variable. It is a variable which surfaces between the time the independent and moderating variable operate to influence the dependent variable.

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