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Andrea M. Landis, PhD, RN UW LEAH Research Designs.

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Presentation on theme: "Andrea M. Landis, PhD, RN UW LEAH Research Designs."— Presentation transcript:

1 Andrea M. Landis, PhD, RN UW LEAH Research Designs

2 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

3 Research Design: Definition and Characteristics The vehicle for hypothesis testing or answering research 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

4 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

5 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?

6 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

7 Threats of Internal Validity History: due to intervening events between pre- and post- 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.

8 Threats of Internal Validity Mortality: due to differences in those who dropped out of a 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 subjects response to being in a study which improves subject performance or behavior

9 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

10 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.

11 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.

12 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 subjects 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.

13 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

14 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

15 Levels of Evidence

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