Research Designs

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Research Designs
Andrea M. Landis, PhD, RN
UW LEAH
Learning Objectives
 Discuss concepts important to research design
 Identify threats of internal validity
 Review different types of non-experimental, experimental,
and quasi-experimental research designs
Research Design: Definition and
Characteristics
 The vehicle for hypothesis testing or answering research
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questions
A blueprint for conducting a study
Maximizes control over factors that could negatively effect
the validity of study findings
Guides the researcher in planning and conducting a study
Links the steps of the research process in the study
Concepts Important to Research
Design
 Causality
 Cause is not directly observable but must be observed
 The cause is necessary for the effect to occur
 Multicausality – recognition that a number of interrelating
variables can be involved in causing a particular effect
 Probability – Addresses the likelihood that something will happen
in a given situation
 Bias
 To slant away from the truth or the expected
 Failing to consider or include both sides of the question or hypothesis
 Control – A check or comparison. Methods to keep the study
conditions constant during the study
Forms of Control
 Manipulation – Researcher exercises by specifying the IV
 Elimination or Inclusion – Holding certain aspects of
intervening and extraneous variables constant
 Statistical – Controlling extraneous variables by including
them in the statistical analysis
 Randomization – Distribution of effects of extraneous
variables via change with assignment of subjects to groups
based on probability
 What is the difference between random sampling and random
assignment?
Concepts Important to Research
Design
 Study Validity – truth or accuracy of the study findings.
 Internal Validity – extent to which the effects detected in the
study are a true reflection of reality.
 External Validity – extent to which the findings of the study
can be generalized to the general population
Threats of Internal Validity
 History: due to intervening events between pre- and post
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test
Maturation: produced by changes in members in one group
which occurred at a different rate than in the comparison
group between data points
Testing: created by repeated measurement
Instrumentation: produced by a change in the measuring
instrument between the pre- and post-test
Selection: differences between the kinds of people in an
experimental group in comparison to the other(s). Due to
lack of random placement of subjects into two groups.
Threats of Internal Validity
 Mortality: due to differences in those who dropped out of a
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particular treatment group versus the comparison group(s)
Ambiguity About the Direction of Causal Influence: occurs when
cause and effect variables are measured at the same time (e.g.,
correlational studies)
Diffusion or Imitation or Treatments: spurious communication of
the treatment to the control group(s)
Compensatory Equalization of Treatments: when the control
group receives the treatment inadvertently because it is seen by
administrators or health care providers to be best for patients
Reactive Effect: produced by a data collector or a subject’s
response to being in a study which improves subject performance
or behavior
Types of Research Designs
 Non-experimental – both randomization and manipulation
absent
 Experimental – both randomization and manipulation
present
 True or classic experiment
 Quasi-experimental – manipulation present, but not
randomization
 One-group (pretest – posttest) design
Major Categories of Non-experimental
Designs
 Descriptive
 Designed to document conditions, attitudes, or characteristics
of individuals or groups
 Exploratory
 Focuses on the relationships among these factors
 Predictive
 Aimed at the development of systems to predict criteria of
interest by utilizing information from one or more predictors
 Explanatory
 Aimed at testing of hypotheses formulated to explain
phenomena of interest. Involves theoretical model testing.
Methods of Non-Experimental
Research
 Retrospective (ex post facto)
 Involves examining data that have been collected in the past, often
obtained from medical records or survey
 Prospective
 Variables are measured through direct recording in the present
 Longitudinal
 Follows a cohort of subjects over time, performing repeated
measurements at prescribed intervals
 Cross-sectional
 Researcher studies a stratified group of subjects at one point in time
and draws conclusions about development within a population by
comparing the characteristics of those strata.
Perspectives in Qualitative Research
Designs
 Phenomenology
 Seeks to draw meaning of experiences through narrative subject
materials. Words like “lived experience” often describe
phenomenological studies.
 Ethnography
 Study of the social milieu of a specific cultural group or people.
Researcher often immersed in subject’s way of life.
 Grounded Theory
 Researcher uses data to develop a theory that will explain what
is observed. Researcher collects, codes, and analyzes data
simultaneously.
Epidemiological Research
 Concerned with the study of the distribution of disease,
injury, or dysfunction in human populations
 Observational Epidemiologic Studies
 Gather measures about disease frequency: prevalence (existing
cases), incidence (new cases)
 Analytic Epidemiologic – Used when enough is known about
a condition to allow testing of hypotheses about the
association of specific risk factors (exposures) and outcomes
 Case-control studies – groups of individuals are selected on the
basis of whether they have the disorder under study
 Cohort studies – group of individuals followed over time to
determine if they will develop a disorder
Nontraditional Designs: Examples
 Methodological Designs
 Used to develop research approaches or the R/V of instruments
to measure constructs used as variables in research
 Secondary Analysis
 Studying data previously collected in another study
 Meta-Analysis Designs
 Involves merging findings from many studies that have
examined the same phenomenon
Levels of Evidence
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