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=== Dependent and Independent Variables ===
=== Dependent and Independent Variables ===
An independent variable, sometimes called an
An independent variable, sometimes called an
experimental or predictor variable, is a variable that is being
experimental or predictor variable, is a variable that is being
dependent variable, sometimes called an outcome variable.
dependent variable, sometimes called an outcome variable.
Imagine that a tutor asks 100 students to complete
Imagine that a tutor asks 100 students to complete
a maths test. The tutor wants to know why some students perform
a maths test. The tutor wants to know why some students perform
dependent and independent variables for the study are:
dependent and independent variables for the study are:
Dependent Variable: Test Mark (measured from 0 to
Dependent Variable: Test Mark (measured from 0 to
100)
100)
Independent Variables: Revision time (measured in
Independent Variables: Revision time (measured in
hours) Intelligence (measured using IQ score)
hours) Intelligence (measured using IQ score)
The dependent variable is simply that, a variable
The dependent variable is simply that, a variable
(this simply doesn't make sense).
(this simply doesn't make sense).
Therefore, the aim of the tutor's investigation is
Therefore, the aim of the tutor's investigation is
to examine whether these independent variables - revision time and IQ
to examine whether these independent variables - revision time and IQ
in some way.
in some way.
In the section on experimental and
In the section on experimental and
non-experimental research that follows, we find out a little more
non-experimental research that follows, we find out a little more
=== Experimental and Non-Experimental Research ===
=== Experimental and Non-Experimental Research ===
Experimental research: In experimental research,
Experimental research: In experimental research,
asked to do 20 hours of revision in the two weeks prior to the test.
asked to do 20 hours of revision in the two weeks prior to the test.
The tutor could then compare the marks that the students achieved.
The tutor could then compare the marks that the students achieved.
Non-experimental research: In non-experimental
Non-experimental research: In non-experimental
understand the different characteristics amongst variables. This is
understand the different characteristics amongst variables. This is
discussed next.
discussed next.
=== Categorical and Continuous Variables ===
=== Categorical and Continuous Variables ===
Categorical variables are also known as discrete
Categorical variables are also known as discrete
or qualitative variables. Categorical variables can be further
or qualitative variables. Categorical variables can be further
categorized as either''' nominal, ordinal or dichotomous.'''
categorized as either''' nominal, ordinal or dichotomous.'''
'''Nominal variables''' are variables that have
'''Nominal variables''' are variables that have
by district. In this case there will be many more levels of the
by district. In this case there will be many more levels of the
nominal variable (30 in fact).
nominal variable (30 in fact).
'''Dichotomous variables''' are nominal
'''Dichotomous variables''' are nominal
"type of property" would be a dichotomous variable.
"type of property" would be a dichotomous variable.
'''Ordinal variables''' are variables that have
'''Ordinal variables''' are variables that have
two or more categories just like nominal variables only the
two or more categories just like nominal variables only the
that "They are OK" is twice as positive as "Not very
that "They are OK" is twice as positive as "Not very
much" for example.
much" for example.
Continuous variables are also known as
Continuous variables are also known as
quantitative variables. Continuous variables can be further
quantitative variables. Continuous variables can be further
categorized as either interval or ratio variables.
categorized as either interval or ratio variables.
'''Interval variables''' are variables for which
'''Interval variables''' are variables for which
20C and 30C is the same as 30C to 40C. However, temperature measured
20C and 30C is the same as 30C to 40C. However, temperature measured
in degrees Celsius or Fahrenheit is NOT a ratio variable.
in degrees Celsius or Fahrenheit is NOT a ratio variable.
'''Ratio variables''' are interval variables but
'''Ratio variables''' are interval variables but
of measurements. So, for example, a distance of ten metres is twice
of measurements. So, for example, a distance of ten metres is twice
the distance of 5 metres.
the distance of 5 metres.
=== Ambiguities in classifying a type of variable ===
=== Ambiguities in classifying a type of variable ===
In some cases, the measurement scale for data is
In some cases, the measurement scale for data is
ordinal but the variable is treated as continuous. For example, a
ordinal but the variable is treated as continuous. For example, a
this is a cause of great dispute.
this is a cause of great dispute.
It is worth noting that how we categorise
It is worth noting that how we categorise
variables is somewhat of a choice. Whilst we categorised gender as a
variables is somewhat of a choice. Whilst we categorised gender as a
continuous variable.
continuous variable.
== Enrichment Activities ==
== Enrichment Activities ==
