Research Design: Using
Quantitative Methods
Objectives
By the end of this session you will be able
to:
• Describe the experimental and quasiexperimental research approaches.
• Formulate appropriate questions and
hypotheses.
• Identify populations and samples.
• Describe the principles of research tool
design (validity and reliability).
Stages in the experimental
design process
Identifying issues
‘Good’ research topics might emerge:
• From the literature.
• Within workplace settings.
• From previous projects/assignments.
• From a sponsor.
Review the literature
What are the
key sources?
What are the major
issues and debates
about the topic?
What are the origins
and definitions of the
topic?
The literature
review of the
research topic
What are the key
theories, concepts
and ideas?
What are the main
questions/problems
that have been
addressed to date?
What is the
epistemological and
ontological basis for
the subject?
Source: adapted from Hart (1998)
Develop questions/hypotheses
Kerlinger and Lee (2000) argues that a good
research question:
• Expresses a relationship between variables
(e.g., company image and sales levels).
• Is stated in unambiguous terms in a question
format, and …
• Must be capable of being operationally
defined (Black, 1993).
Types of applied research
questions – with examples
Type of research question
Example
Descriptive
How common is drug use amongst
university students?
Normative
How serious is drug abuse
amongst university students
Correlation
What is the relationship between
gender, academic performance
and drug use amongst university
students?
Impact
Has the drug awareness campaign
had any impact on the level of
university student drug use?
A hypothesis
• Is a speculative statement of the relation
between two or more variables.
• Describes a research question in a
testable format which predicts the nature
of the answer.
• Can be written as a directional statement,
such as, ‘When this happens, then that
happens’.
Identifying independent and
dependent variables
• Dependent variables - a variable that forms the focus of
research, and depends on another (the independent or
explanatory) variable.
• Independent variable - used to explain or predict a result
or outcome on the dependent variable.
• Intervening variable – a hypothetical internal state, used
.
to explain relationship between two observed variables.
Conducting the study
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Planning the design.
Gathering data.
Storing data.
Observing ethical
guidelines.
Using descriptive and inferential
statistics
Descriptive statistics
90
80
70
60
50
East
West
North
40
30
20
10
0
1st 2nd 3rd 4th
Qtr Qtr Qtr Qtr
Inferential statistics e.g.
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T-test data
Mann-Whitney U data
Chi-square data
Spearman’s rho data
Pearson Product
Moment data
• ANOVA
Accept or reject the hypothesis
• A hypothesis cannot be ‘proved’ to be right
– all theories are provisional/tentative (until
disproved).
• Acceptance or rejection of the hypothesis
based upon the weight of statistical
evidence and probability entails:
– The risk of accepting the hypothesis as true
(when it is in fact false).
– The risk of rejecting the hypothesis as false
(when it is in fact true).
Preparing the formal report
Why the study was conducted
What research questions and
hypotheses were evaluated
How questions were turned
into a research design
What differences were observed
between the hypotheses
and the results
What conclusions can be drawn –
do these support or contradict the
hypothesis and existing theories?
Experimental design
• The researcher has control over the
experiment in terms of:
– Who is being researched (subjects randomly
assigned).
– What is being researched.
– When the research is to be conducted.
– Where the research is to be conducted.
– How the research is to be conducted.
Typically, researchers often have no control over the ‘who’, having
to use pre-existing groups – hence, a quasi-experimental design.
Quasi-experimental designs
Quasi-experimental designs are best used when:
• Randomization is too expensive, unfeasible to
attempt or impossible to monitor closely.
• There are difficulties, including ethical
considerations, in withholding the treatment.
• The study is retrospective and the programme
being studied is already underway.
Differences in quantitative
research design
Differences between experimental, quasiexperimental and non-experimental research
Faulty quantitative designs
One group, pre-test/post-test problems:
• Maturation effects
• Measurement procedures
• Instrumentation
• Experimental mortality
• Extraneous variables
Sound quantitative designs (1)
Experimental group with control
Sound quantitative designs (2)
Quasi-experimental design with nonequivalent control
Generalizing from samples to
populations
To generalize, samples
must be representative
of the population,
through:
• Random probability
sampling (but note
problem of sampling
error).
Types of probability sample
• Simple random sample (where the
sampling frame is equal to the population).
• Stratified random sample (sampling from
strata according to some characteristic
e.g., geographical area, age, gender).
• Cluster sample (e.g., a county, households
in a street, schools in a town, etc.)
• Stage sample (cluster sample followed by
random selection from cluster).
Non-random sampling
• Purposive: Subjects selected against one
or more trait.
• Quota: Non-random selection of subjects
from identified strata until the planned
number of subjects is reached.
• Convenience or volunteer.
• Snowball: Researcher identifies a small
number of subjects, who, in turn, identify
others in the population.
Instrument design: validity
• Internal validity: The extent to which changes in
the dependent variable can be attributed to the
independent variable.
• External validity: This is the extent to which it is
possible to generalize from the data to a larger
population or setting.
• Criterion validity: How people have answered a
new measure of a concept, with existing, widely
accepted measures of a concept .
• Construct validity: The measurement of abstract
concepts and traits, such as ability, anxiety,
attitude, knowledge, etc.
Instrument design: reliability
Reliability is the consistency between two
measures of the same thing such as:
• Two separate instruments.
• Two like halves of an instrument (for
example, two halves of a questionnaire).
• The same instrument applied on two
occasions.
• The same instrument administered by two
different people.
Summary
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Experimental research generally comprises two stages: the planning stage
and the operational stage.
Experimental research begins from a priori questions or hypotheses that the
research is designed to test.
Research questions should express a relationship between variables. A
hypothesis is predictive and capable of being tested.
Dependent variables are what experimental research designs are meant to
affect through the manipulation of one or more independent variables.
In a true experimental design the researcher has control over the
experiment: who, what, when, where and how the experiment is to be
conducted. This includes control over the who of the experiment – that is,
subjects are assigned to conditions randomly.
Where any of these elements of control is either weak or lacking, the study
is said to be a quasi-experiment.
In true experiments, it is possible to assign subjects to conditions, whereas
in quasi-experiments subjects are selected from previously existing groups.
Research instruments need to be both valid and reliable. Validity means
that an instrument measures what it is intended to measure. Reliability
means that an instrument is consistent in this measurement