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.
