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 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 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 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