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Chapter 8

Introduction to Quantitative Research

Research Design

Provides the plan or blueprint
Is the vehicle for systematically testing research questions and hypotheses
Provides the structure for maintaining the control in the study

Research Design Purpose

Achieved with steps taken by the researcher to hold the conditions of the study uniform and avoid or decrease the effect of intervening, extraneous, or mediating variables on the dependent variable or outcome
Avoids bias or threats to the internal validity of the study

Control

Intervention fidelity
Intervention fidelity means that the researcher standardized the intervention and planned how to administer the intervention to each subject in the same manner under the same conditions.

Control (Cont.)

Objectivity in conceptualization of the research question
Type of design chosen
Accuracy
Feasibility
Control and intervention fidelity
Validity: internal and external

Considerations in Quantitative Research

Objectivity can be achieved from a thorough review of the literature and the development of a theoretical framework.
The literature review should be presented so that the reader can judge the objectivity of the research question.

Objectivity in Conceptualization of the Research Question

Accomplished through the theoretical framework and literature review
All aspects of the study systematically and logically follow from the research question
Pilot study

Accuracy

Fidelity—trustworthiness or faithfulness
Intervention fidelity (treatment fidelity)—researcher standardized the intervention and planned how to administer the intervention to each subject in the same manner under the same conditions

Control and Intervention Fidelity

Ruling out mediating or intervening variables that compete with the independent variables as an explanation for a study’s outcome
Extraneous, mediating, or intervening variable— occurs between the independent and dependent variable and interferes with interpretation of the dependent variable

Control

Similarity with respect to the extraneous variables relevant to the particular study

Homogenous Sample

Participants in the study are homogeneous or have similar extraneous variables that might affect the dependent variable.
Homogeneity of the sample limits generalizability or the potential to apply the results of a study to other populations.

Homogeneity

Data-collection procedures should reflect a cookbook-like recipe of how the researcher controlled the study’s conditions.
Environmental conditions, timing of data collection, data-collection instruments, and data-collection procedures used to collect the data are the same for each subject.
Intervention fidelity.

Constancy in Data Collection

Design
Training
Delivery
Receipt
Enactment

Constancy in Data Collection (Cont.)

The independent variable is:
The variable that the researcher hypothesizes will have an effect on the dependent variable
Experimental or interventional group
Usually manipulated (experimental study) but sometimes cannot be manipulated (nonexperimental)

Manipulated Independent Variable

The independent variable is:
Manipulated by means of a program, treatment, or intervention done to only one group in the study (experimental group)
The control group gets the standard treatment or no treatment

Independent Variable

The dependent variable is:
A factor, trait, or condition that can exist in differing amounts or types
Not manipulated and presumed to vary with changes in the independent variable
The variable the researcher is interested in explaining

Dependent Variable

Each subject in the study has an equal chance of being assigned to the control group or the experimental group.
Randomization assumes that any important intervening, extraneous, or mediating variable will be equally distributed between the groups, minimizing variance and decreasing selection bias.

Randomization

Asks whether the independent variable really made the difference or the change in the dependent variable
Established by ruling out other factors or threats as rival explanations

Internal Validity

History
An event, other than the intervention, that might have an effect on the dependent variable; the event could be either inside or outside the experimental setting

Threats to Internal Validity

Maturation
Developmental, biological, or psychological processes that operate within an individual over time. These processes are outside the experimental setting.

Threats to Internal Validity (Cont.)

Testing
Taking the same test more than once can influence the participant’s responses the next time the test is taken

Threats to Internal Validity (Cont.)

Instrumentation
Changes in equipment used to make measurements or changes in observational techniques may cause measurements to vary between participants related to treatment fidelity

Threats to Internal Validity (Cont.)

Mortality
The loss of study subjects
Selection bias
A partiality in choosing the participants in a study

Threats to Internal Validity (Cont.)

Questions the conditions under which the findings are generalized
Deals with the ability to generalize the findings outside the study to other populations and environments

External Validity

Selection effects
What method was used to select the sample? How were subjects assigned to groups?
Reactive effects
Subjects’ responses to being studied
Hawthorne effect

Threats to External Validity

Measurement effects
A pretest may act like an intervention and influence or change the subjects’ responses

Threats to External Validity (Cont.)

Is the type of design used appropriate?
Does the researcher use the various concepts of control that are consistent with the type of design chosen?
Does the design used seem to reflect the issues of economy?

Critiquing Criteria for Quantitative Studies

Does the design used seem to flow from the proposed research question, theoretical framework, literature review, and hypothesis?
What are the threats to internal validity?
What are the controls for the threats to internal validity?

Critiquing Criteria for Quantitative Studies (Cont.)

What are the threats to external validity?
What are the controls for the threats to external validity?
Is the design appropriately linked to the evidence hierarchy?

Critiquing Criteria for Quantitative Studies (Cont.)

College males, ages 18 to 23

Online, 1:1, or class sessions

Maslow’s hierarchy of needs theory

Which type of education leads to sustained cessation?

Which component creates the research design in a tobacco cessation study?

ANSWER: C

RATIONALE: Maslow’s Hierarchy of Needs theory. The research process does not need to be a sterile procedure, but rather one where the researcher develops a masterful work within the limits of a research question and the related theoretical basis. The framework that the researcher creates is the design.

A thorough literature review

Compare only online and 1:1 sessions

Complete a pilot study with a very small sample first

Remove external variables

To increase accuracy in the previous example, which might the new researcher consider first?

ANSWER: B

RATIONALE: Compare only online and 1:1 sessions. To increase accuracy, a beginning researcher may answer a question involving a few variables that will not require the use of sophisticated designs. The simplicity of a research project does not render it useless or of a lesser value for practice. A helps objectivity in conceptualization of the research question, C helps feasibility control, and D, intervention fidelity. All external variables cannot be removed, only controlled.

A college health center identifies lack of testicular self-examination among students and implements an intense summer wellness program focusing on the benefits of testicular self-examination. Afterward, a count indicates an increased number of students who do not complete testicular self-examinations

History

Maturation

Testing

Mortality

Selection bias

Which internal validity threat is suspected in the following scenario?

ANSWER: D

RATIONALE: Mortality, the loss of study subjects from the first data-collection point (pretest) to the second data-collection point (posttest). If the subjects who remain in the study are not similar to those who dropped out, the results could be affected. The college community has a high rate of turnover during the summer.

A nurse researcher is investigating the effects of yoga and blood pressure. One group of subjects is participating in a yoga class and the other group is not.

Qualitative

Correlational

Meta-analysis

Experimental

Which type of research design should be used in the following scenario?

ANSWER: D

RATIONALE: Experimental designs are used to compare treatment group with control group. Qualitative designs are used when there is little or no research or literature available for the area being investigated. Correlational studies look at the relationship between or among variables. Meta-analysis involves results of multiple studies.