Page 52 - DMGT209_QUANTITATIVE_TECHNIQUES_II

Unit 3: Language of Research

Variables are created with a name, type, and shape before they are assigned data values, so a Notes
variable may exist with no values. The value of an attribute is specified when it is created, unless
it is a zero-length attribute.
A variable may have attributes, but an attribute cannot have attributes. Attributes assigned to
variables may have the same units as the variable (for example, valid-range) or have no units
(for example, scale-factor). If you want to store data that requires units different from those of
the associated variable, it is better to use a variable than an attribute.

3.3.3 Dependency

Another important distinction having to do with the term ‘variable’ is the distinction between
an independent and dependent variable. This distinction is particularly relevant when you are
investigating cause-effect relationships.

The terms dependent and independent variables are used to distinguish between two types of
quantities being considered, separating them into those available at the start of a process and
those being created by it, where the latter (dependent variables) are dependent on the former
(independent variables).
In a research experiment, the dependent variable (DV) is the event studied and expected to
change whenever the independent variable is altered.
In the design of experiments, an independent variable’s values are controlled or selected by the
experimenter to determine its relationship to an observed phenomenon (i.e., the dependent
variable). In such an experiment, an attempt is made to find evidence that the values of the
independent variable determine the values of the dependent variable. The independent variable
(IV) can be changed as required, and its values do not represent a problem requiring explanation
in an analysis, but are taken simply as given.

!
Caution The dependent variable, usually cannot be directly controlled.

Controlled variables are also important to identify in experiments. They are the variables that
are kept constant to prevent their influence on the effect of the independent variable on the
dependent. Every experiment has a controlling variable, and it is necessary to not change it, or
the results of the experiment won’t be valid.
“Extraneous variables” are those that might affect the relationship between the independent
and dependent variables. Extraneous variables are usually not theoretically interesting. They
are measured in order for the experimenter to compensate for them.

Example: An experimenter who wishes to measure the degree to which caffeine intake
(the independent variable) influences explicit recall for a word list (the dependent variable)
might also measure the participant’s age (extraneous variable). He can then use these age data to
control for the uninteresting effect of age, clarifying the relationship between caffeine and
memory.
In summary:

1. Independent variables answer the question “What do I change?”
2. Dependent variables answer the question “What do I observe?”
3. Controlled variables answer the question “What do I keep the same?”

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