Research Methods STA630
VARIABLES AND TYPES OF VARIABLES
Variable is central idea in research. Simply defined, variable is a concept that varies. There are two
types of concepts: those that refer to a fixed phenomenon and those that vary in quantity, intensity, or
amount (e.g. amount of education). The second type of concept and measures of the concept are
variables. A variable is defined as anything that varies or changes in value. Variables take on two or
more values. Because variable represents a quality that can exhibit differences in value, usually
magnitude or strength, it may be said that a variable generally is anything that may assume different
numerical or categorical values. Once you begin to look for them, you will see variables everywhere.
For example gender is a variable; it can take two values: male or female. Marital status is a variable; it
can take on values of never married, single, married, divorced, or widowed. Family income is a
variable; it can take on values from zero to billions of Rupees. A person's attitude toward women
empowerment is variable; it can range from highly favorable to highly unfavorable. In this way the
variation can be in quantity, intensity, amount, or type; the examples can be production units,
absenteeism, gender, religion, motivation, grade, and age. A variable may be situation specific; for
example gender is a variable but if in a particular situation like a class of Research Methods if there are
only female students, then in this situation gender will not be considered as a variable.
Types of Variable
1. Continuous and Discontinuous variables
Variables have different properties and to these properties we assign numerical values. If the values of a
variable can be divided into fractions then we call it a continuous variable. Such a variable can take
infinite number of values. Income, temperature, age, or a test score are examples of continuous
variables. These variables may take on values within a given range or, in some cases, an infinite set.
Any variable that has a limited number of distinct values and which cannot be divided into fractions, is a
discontinuous variable. Such a variable is also called as categorical variable or classificatory variable,
or discrete variable. Some variables have only two values, reflecting the presence or absence of a
property: employed-unemployed or male-female have two values. These variables are referred to as
dichotomous. There are others that can take added categories such as the demographic variables of race,
All such variables that produce data that fit into categories are said to be
discrete/categorical/classificatory, since only certain values are possible. An automotive variable, for
example, where "Chevrolet" is assigned a 5 and "Honda" is assigned a 6, provides no option for a 5.5
(i.e. the values cannot be divided into fractions).
2. Dependent and Independent Variables
Researchers who focus on causal relations usually begin with an effect, and then search for its causes.
The cause variable, or the one that identifies forces or conditions that act on something else, is the
independent variable. The variable that is the effect or is the result or outcome of another variable is the
dependent variable (also referred to as outcome variable or effect variable). The independent variable is
"independent of" prior causes that act on it, whereas the dependent variable "depends on" the cause.
It is not always easy to determine whether a variable is independent or dependent. Two questions help
to identify the independent variable. First, does it come before other variable in time? Second, if the
variables occur at the same time, does the researcher suggest that one variable has an impact on another
variable? Independent variables affect or have an impact on other variables. When independent
variable is present, the dependent variable is also present, and with each unit of increase in the
independent variable, there is an increase or decrease in the dependent variable also. In other words, the
variance in dependent variable is accounted for by the independent variable. Dependent variable is also
referred to as criterion variable.
Research Methods STA630
In statistical analysis a variable is identified by the symbol (X) for independent variable and by the
symbol (Y) for the dependent variable. In the research vocabulary different labels have been associated
with the independent and dependent variables like:
Predicted from ...
Predicted to ...
Research studies indicate that successful new product development has an influence on the stock market
price of a company. That is, the more successful the new product turns out to be, the higher will be the
stock market price of that firm. Therefore, the success of the
New product is the independent variable, and stock market price the dependent variable.
The degree of perceived success of the new product developed will explain the variance in the stock
market price of the company.
It is important to remember that there are no preordained variables waiting to be discovered "out there"
that are automatically assigned to be independent or dependent. It is in fact the product of the
researcher's imagination demonstrated convincingly.
3. Moderating Variables
A moderating variable is one that has a strong contingent effect on the independent variable-dependent
variable relationship. That is, the presence of a third variable (the moderating variable) modifies the
original relationship between the independent and the dependent variable.
For example, a strong relationship has been observed between the quality of library facilities (X) and the
performance of the students (Y). Although this relationship is supposed to be true generally, it is
nevertheless contingent on the interest and inclination of the students. It means that only those students
who have the interest and inclination to use the library will show improved performance in their studies.
In this relationship interest and inclination is moderating variable i.e. which moderates the strength of
the association between X and Y variables.
4. Intervening Variables
A basic causal relationship requires only independent and dependent variable. A third type of variable,
the intervening variable, appears in more complex causal relationships. It comes between the
independent and dependent variables and shows the link or mechanism between them. Advances in
knowledge depend not only on documenting cause and effect relationship but also on specifying the
mechanisms that account for the causal relation. In a sense, the intervening variable acts as a dependent
variable with respect to independent variable and acts as an independent variable toward the dependent
A theory of suicide states that married people are less likely to commit suicide than single people. The
assumption is that married people have greater social integration (e.g. feelings of belonging to a group
or family). Hence a major cause of one type of suicide was that people lacked a sense of belonging to
group (family). Thus this theory can be restated as a three-variable relationship: marital status
(independent variable) causes the degree of social integration (intervening variable), which affects
suicide (dependent variable). Specifying the chain of causality makes the linkages in theory clearer and
helps a researcher test complex relationships.
Look at another finding that five-day work week results in higher productivity. What is the process of
moving from the independent variable to the dependent variable? What exactly is that factor which
theoretically affects the observed phenomenon but cannot be seen? Its effects must be inferred from the
effects of independent variable on the dependent variable. In this work-week hypothesis, one might
Research Methods STA630
view the intervening variable to be the job satisfaction. To rephrase the statement it could be: the
introduction of five-day work week (IV) will increase job satisfaction (IVV), which will lead to higher
5. Extraneous Variables
An almost infinite number of extraneous variables (EV) exist that might conceivably affect a given
relationship. Some can be treated as independent or moderating variables, but most must either be
assumed or excluded from the study. Such variables have to be identified by the researcher. In order to
identify the true relationship between the independent and the dependent variable, the effect of the
extraneous variables may have to be controlled. This is necessary if we are conducting an experiment
where the effect of the confounding factors has to be controlled. Confounding factors is another name
used for extraneous variables.
Relationship among Variables
Once the variables relevant to the topic of research have been identified, then the researcher is interested
in the relationship among them. A statement containing the variable is called a proposition. It may
contain one or more than one variable. The proposition having one variable in it may be called as
univariate proposition, those with two variables as bivariate proposition, and then of course multivariate
containing three or more variables. Prior to the formulation of a proposition the researcher has to
develop strong logical arguments which could help in establishing the relationship. For example, age at
marriage and education are the two variables that could lead to a proposition: the higher the education,
the higher the age at marriage. What could be the logic to reach this conclusion? All relationships have
to be explained with strong logical arguments.
If the relationship refers to an observable reality, then the proposition can be put to test, and any testable
proposition is hypothesis.
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