MSN5300Week 5Faculty: Dr. K. Richards

Chapters 10, 11

Quantitative Research Designs

At the end of this class, students will be able to:

analyze relationship between research question and choice of research design;

distinguish between interventional and non-interventional research methods;

differentiate between descriptive and correlational research designs; and

describe 3 essential elements of experimental research.

Methodology

represents the major type of research used for a study

quantitative

qualitative

both

Quantitative Design

researcher’s choice of the best way to answer the research question

interventional versus noninterventional designs

Interventional design

– tests effect of an intentional action (intervention) on a measured result (outcome)

– experimental designs, quasi-experimental designs

Noninterventional design

– counts and measures characteristics about the phenomenon of interest and the study variables without intervention.

– descriptive designs, correlational designs

answer to research question comes from statistical analysis of numerical data

Quantitative Design (…con’t…)

Methods

details of the proposed research

include:

recruitment site(s) selected

subjects:

who

inclusion/exclusion criteria

how recruited and consented

data collection:

tools to be used

how data will be collected

how any interventions will be enacted

how data will be organized

data analysis:

how data will be analyzed

Methods

Random Selection Versus Random Assignment

random selection:

every element in the accessible population has an equal change of being selected

study results likely to be generalizable to the accessible population (good external validity)

random assignment:

subjects are assigned to one of the study groups, and every subject has the chance of being in a certain group

groups are very similar to one another (good internal validity)

Control Versus Comparison Groups

Experimental:

randomly assigned controls for the effects of extraneous variables

Quasi-experimental:

may or may not control

if they do control, groups are properly termed nonrandom control groups

if they do not control, they are comparison groups

Key Terms

causality

multiple

causality

probability

bias

measurement

manipulation

control

prospective versus

retrospective

validity

Causality

cause-and-effect relationship

interventional research tests causality

noninterventional research does not

correlation is not causation

Multiple Causality

2 or more variables combine to cause an effect

Probability

Probabilities:

likelihoods

expressed as percentages

Prediction

usually based on probabilities

offering an opinion or guess about an unknown or future event, amount, outcome, or result

Bias

to slant away from the true or expected, leaning to one side

potential sources:

operational definitions

measurement methods

researcher

study subjects

study sample

data

identify in advance to avoid tainting data

Measurement

value is assigned to variable

must apply to the concept studied

quality of raw data collected determined by:

choice of instrument

validity

reliability

Manipulation

move around or control

synonym for intervention

Answer: A

interventional research:

independent variable

also refers to control for the effects of potentially extraneous variables

noninterventional research:

enacted through:

determining exclusion criteria

operationalizing variables carefully

Control

Prospective Versus Retrospective

prospective = looking forward, “real time”

retrospective = looking backward

data collected and recorded in the past:

existent databases

previously collected research data

audit data

both retrospective and prospective data collection are appropriate for noninterventional research

External Validity

design-resultant decisions that affect the population to which research results can be generalized

due in large part to sampling strategy

random sampling enhances external validity

Statistical Conclusion Validity

correctness of the decisions that the researcher makes regarding statistical tests

selection of an adequately large sample so that true relationships among variables are revealed

use of the correct statistical tests, given the nature of the study variables

power analysis to avoid the threat of low statistical power in noninterventional research

Non-Interventional Research Designs

Descriptive Research

conducted in a natural setting

answers research question r/t incidence, prevalence, or frequency of occurrence of a phenomenon of interest

may be prospective or retrospective

Descriptive Design

describes phenomenon of interest and its component variables within one single subject group, sometimes called a cohort

Comparative Descriptive Design

two distinct groups are described and compared in terms of their respective variables

Longitudinal Designs

examine changes in the same subjects over time

may use correlational statistical methods, such as linear regression

if retrospective, data reflect measured increments of time in the past

Cross Sectional Designs

examine change over time different groups of subjects

purpose is to examine changes in a variable over time by comparing its value in several groups that are in different phases of a process

Interventional Research Designs

Treatment Fidelity

study intervention (treatment) must be chosen so that treatment fidelity can be maintained

treatment must be described fully so that research assistants or agency personnel know exactly how it is to be applied

treatment fidelity is easier when data collection occurs over a short time and number of data-collectors is few

Other Controls

Controlling measurement:

reliability and validity of all measurement tools provided in the research report

measures of dependent variables must be consistently implemented

Experimental Research

design:

pretest-posttest control group design

Pretest-Posttest Control Group Design

“true” experimental design

random assignment of consented subjects to either treatment or control group

measurement of dependent variables in all subjects

application of the intervention to treatment group only

post-intervention remeasurement of dependent variable again in all subjects

Quasi-Experimental Research

used when experimental design cannot or should not be used

lacking at least one attribute of experimental design:

researcher-controlled manipulation of the independent variable, or

traditional type of control group, or

random assignment of subjects to groups

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