Variables

A variable is a concept—a noun that stands for variation within a class of objects, such as chair, gender, eye color, achievement, motivation ,or running speed. Even spunk, style, and lust for life are variables. Notice that the individual members in the class of objects, however, must differ or vary to qualify the class as a variable. If all members of a class are identical, we do not have a variable. Such characteristics are called constants, since the individual members of the class are not allowed to vary, but rather are held constant. In any study, some characteristics will be variables, while others will be constants.

An example may make this distinction clearer. Suppose a researcher is interested in studying the effects of reinforcement on student achievement. The researcher systematically divides a large group of students, all of whom are ninth-graders, into three smaller subgroups. She then trains the teachers of these subgroups to reinforce their students in different ways (one gives verbal praise, the second gives monetary rewards, the third gives extra points) for various tasks the students perform. In this study, reinforcement would be a variable (it contains three variations), while the grade level of the students would be a constant.

There are many certain variables that can be investigated:

    A.    QUANTITATIVE VERSUS CATEGORICAL VARIABLES

Quantitative variables exist in some degree (rather than all or none) along a continuum from less to more, and we can assign numbers to different individuals or objects to indicate how much of the variable they possess. categorical variables do not vary in degree, amount, or quantity but are qualitatively different.

Examples include eye color, gender, and religious preference, and occupation, position on a baseball team, and most kinds of research “treatments” or “methods.” For example, suppose a researcher wishes to compare certain attitudes in two different groups of voters, one in which each individual is registered as a member of one political party and the other in which individuals are members of another party.

   B.     INDEPENDENT VERSUS DEPENDENT VARIABLES

Independent variables are those that the researcher chooses to study in order to assess their possible effect(s) on one or more other variables. An independent variable is presumed to affect (at least partly cause) or somehow influence at least one other variable. The variable that the independent variable is presumed to affect is called a dependent variable. In commonsense terms, the dependent variable “depends on” what the independent variable does to it, how it affects it. For example, a researcher studying the relationship between childhood success in mathematics and adult career choice is likely to refer to the former as the independent variable and subsequent career choice as the dependent variable. Amoderator variable

influences the direction and strength of the relationship between two variables, such as an independent and dependent variable. Amediator variable explains the relationship between the two variables. As an example, consider the relationship between the desire to quit a particular job and being a good company citizen. Age may be a moderator, in that the associate between desire to quit and company citizenship could be stronger for older employees than for young employees

   C.     MODERATOR VARIABLES

A moderator variable is a special type of independent variable. It is a secondary independent variable that has been selected for study in order to determine if it affects or modifies the basic relationship between the primary independent variable and the dependent variable. Thus, if an experimenter thinks that the relationship between variables X and Y might be altered in some way by a third variable Z, then Z could be included in the study as a moderator variable. While a moderator variable can modify or influence the strength of a relationship between two other variables, a mediator variable is one that attempts to explain the relationship between the two other variables.  

   D.    EXTRANEOUS VARIABLES

Extraneous variables are independent variables that have not been controlled. There are many possible extraneous variables. The personality of the teachers involved, the experience level of the students, the time of day the classes are taught, the nature of the subject taught, the textbooks used, the type of learning activities the teachers employ, and the teaching methods—all are possible extraneous variables that could affect learning in this study.