Andrea M. Landis, PhD, RN
UW LEAH
Research Designs
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 andCharacteristics
The vehicle for hypothesis testing or answering researchquestions
A blueprint for conducting a study
Maximizes control over factors that could negatively effectthe 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 ResearchDesign
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 interrelatingvariables can be involved in causing a particular effect
Probability – Addresses the likelihood that something will happenin 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 studyconditions constant during the study
Forms of Control
Manipulation – Researcher exercises by specifying the IV
Elimination or Inclusion – Holding certain aspects ofintervening and extraneous variables constant
Statistical – Controlling extraneous variables by includingthem in the statistical analysis
Randomization – Distribution of effects of extraneousvariables via change with assignment of subjects to groupsbased on probability
What is the difference between random sampling and randomassignment?
Concepts Important to ResearchDesign
Study Validity – truth or accuracy of the study findings.
Internal Validity – extent to which the effects detected in thestudy are a true reflection of reality.
External Validity – extent to which the findings of the studycan be generalized to the general population
Threats of Internal Validity
History: due to intervening events between pre- and post-test
Maturation: produced by changes in members in one groupwhich occurred at a different rate than in the comparisongroup between data points
Testing: created by repeated measurement
Instrumentation: produced by a change in the measuringinstrument between the pre- and post-test
Selection: differences between the kinds of people in anexperimental group in comparison to the other(s). Due tolack of random placement of subjects into two groups.
Threats of Internal Validity
Mortality: due to differences in those who dropped out of aparticular treatment group versus the comparison group(s)
Ambiguity About the Direction of Causal Influence: occurs whencause and effect variables are measured at the same time (e.g.,correlational studies)
Diffusion or Imitation or Treatments: spurious communication ofthe treatment to the control group(s)
Compensatory Equalization of Treatments: when the controlgroup receives the treatment inadvertently because it is seen byadministrators or health care providers to be best for patients
Reactive Effect: produced by a data collector or a subject’sresponse to being in a study which improves subject performanceor behavior
Types of Research Designs
Non-experimental – both randomization and manipulationabsent
Experimental – both randomization and manipulationpresent
True or classic experiment
Quasi-experimental – manipulation present, but notrandomization
One-group (pretest – posttest) design
Major Categories of Non-experimentalDesigns
Descriptive
Designed to document conditions, attitudes, or characteristicsof individuals or groups
Exploratory
Focuses on the relationships among these factors
Predictive
Aimed at the development of systems to predict criteria ofinterest by utilizing information from one or more predictors
Explanatory
Aimed at testing of hypotheses formulated to explainphenomena of interest. Involves theoretical model testing.
Methods of Non-ExperimentalResearch
Retrospective (ex post facto)
Involves examining data that have been collected in the past, oftenobtained from medical records or survey
Prospective
Variables are measured through direct recording in the present
Longitudinal
Follows a cohort of subjects over time, performing repeatedmeasurements at prescribed intervals
Cross-sectional
Researcher studies a stratified group of subjects at one point in timeand draws conclusions about development within a population bycomparing the characteristics of those strata.
Perspectives in Qualitative ResearchDesigns
Phenomenology
Seeks to draw meaning of experiences through narrative subjectmaterials. Words like “lived experience” often describephenomenological 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 whatis observed. Researcher collects, codes, and analyzes datasimultaneously.
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 (existingcases), incidence (new cases)
Analytic Epidemiologic – Used when enough is known abouta condition to allow testing of hypotheses about theassociation of specific risk factors (exposures) and outcomes
Case-control studies – groups of individuals are selected on thebasis of whether they have the disorder under study
Cohort studies – group of individuals followed over time todetermine if they will develop a disorder
Nontraditional Designs: Examples
Methodological Designs
Used to develop research approaches or the R/V of instrumentsto 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 haveexamined the same phenomenon
Levels of Evidence
