RESEARCH DESIGNS Janice Long, PhD, RN Patricia Hart, PhD, RN

Definition of Design • Research design is the master plan that

guides and holds together all the major parts of the research project to address the central research questions. • samples or groups • measures • treatments or programs • time elements

Choosing a Design • The research problem dominates the design. • The design you choose is based on the problem or research

question you want to answer and how much you know about the problem.

Research Problem/Question

Data

Methods

Basics of Design Quantitative

Qualitative

Objective Deductive Generalizable

Subjective Inductive Not generalizable (transferrable) Uses Words

Uses Numbers

Mixed Methods Can use parts of both

Types of Design Exploratory

Descriptive

• Clarify the

• Answers

problem • Define terms • Get background information • Establish research priorities

questions about who, what, when, where and how. • Two basic types: • Cross- Sectional • Longitudinal

Causal •

If the program or treatment is given, then the outcome occurs

Or •

If the program/treatment is not given, then the outcome does not occur • Answers question about why

Exploratory Design • May be quantitative or qualitative • Secondary Data Analysis • Focus Groups • Case Analyses • Surveys • Interviews

Descriptive Design • Does not include researcher imposed treatments • Examines variables in their natural environment • Time • Cross-Sectional Studies measure across one point in time

• Longitudinal Studies measure across time

• Correlation • Comparison across groups • Comparison within groups

Causal • Experimental • Examines cause and effect • Uses random assignment to groups • Quasi-experimental • Random assignment to groups is not used but a control group or multiple measures used

Trochim & Donnelly, 2009

Threats to Validity in Quantitative Studies • Internal Validity • The extent to which it is possible to make an inference that the independent variable, rather than another factor, is truly causing variation in the dependent variable1,p.244 • Meaning • Has to do with how the study was set up and conducted including how the participants were selected and “managed” once they were in the study

Threats to Validity in Quantitative Studies • External Validity • The extent to which it can be inferred that relationships observed in a study hold true over variations in people, conditions, and settings, as well as over variations in treatments and outcomes1,p350 • Meaning • Has to do with our ability to say if the researchers’ findings would be useful with a similar group or people, This is called generalizability

Threats to Internal Validity Threat

What it means

What kind of study is most likely to be effected

Strategies

Temporal Ambiguity

Is the independent variable really coming before the dependent variable

Comparative & correlational designs

Understanding of the variables under study

History

The occurrence of external events that take place concurrently with the IV, and that can affect the outcomes.

Longitudinal & Repeated Measures studies.

Randomization Control group

Maturation

Processes occurring within participants during the course of the study as a result of the passage of time rather than as a result of the IV. Participants get older, wiser, more depressed, more hungry, more tired.

Longitudinal studies where the participants are more likely to change such as adolescents, infants, or people who are quite ill.

Randomization Control group

Threats to Internal Validity Threat

What it means

What kind of study is most likely to be effected

Strategies

Testing

Occurs when a pretest influences the way subjects respond on a post test.

Repeated measures or a pretest-post-test design

Control group

Instrumentation

Changes made in the way the variable is measured, i.e, BP. Data collectors get better or worse at what they are doing.

Physiologic instruments or those in which researchers are collecting the data in person.

Regular calibration, use of multiple observers, training of observers establishment of reliability, validity, and objectivity of measurement procedures

Threats to Internal Validity Threat

What it means

What kind of study is most likely to be effected

Strategies

Selection

Pre-existing differences Quasi-experimental studies between the participants and convenience samples. selected for a study or those who volunteer for the study & those not in the study.

Random selection Random assignment Control group

Mortality/Attrition

Participants drop out of a study or are lost to follow up

Subject matching & omission

Longitudinal studies.

Threats to External Validity Threat

What it means

What kind of study is most likely to be effected

Strategies

Reactivity

The influence of participating in a study on the responses of subjects. (Hawthorne effect: Participants’ behaviors affected by personal values or desires t please the experimenter). Researcher may inadvertently affect how intervention conducted or how they interact with participants.

Any study with pre-test.

Inform the subjects of their roles, Double-blind experimental designs

Effects of Selection

Sample does not reflect the general population

Convenience samples

Randomization

Threats to External Validity Threat

What it means

What kind of study is most likely to be effected

Strategies

Interaction of Treatment & Selection of Subjects

Where the independent variable might not affect individuals the same way

Convenience samples

Random selection Random assignment Control group Subject matching

Interaction of Treatment & Setting

When the intervention in one setting cannot be generalized using the same intervention

Studies related to the same phenomenon which used similar types of hospitals

Use diverse sample populations when conducting studies

Interaction of Treatment & History

When external events affect the intervention

Studies in which the intervention is likely to have changed or the targeted populations may have changed

Randomization Control group Replication studies

QUESTIONS

References • Norwood, S. L. (2009). Research essentials: Foundations

for evidence-based practice. Upper Saddle River, NJ: Pearson Education, Inc. • Polit, D. F., & Beck, C. T. (2012). Nursing research: Generating and assessing evidence for nursing practice. (9th ed.). Philadelphia, PA: Lippincott, Williams, & Wilkins. • Schmidt, N. A., & Brown, J. M. (2012). Evidence-based practice for nurses: Appraisal and application of research (2nd ed.). Sudbury, MA: Jones & Bartlett Learning • Trochim & Donnelly (2009) The research methods knowledge base. Retrieved from http://www.socialresearchmethods.net/kb/destypes.php