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Chapter 9

Quantitative Research Design

Question

Tell whether the following statement is true or false:

Many qualitative nursing studies aim to elucidate cause-and-effect relationships.

Answer

False

Many quantitative not qualitative nursing studies aim to elucidate cause-and-effect relationships.

Question

Tell whether the following statement is true or false:

Counterfactual is what would have happened to the same people simultaneously exposed and not exposed to the causal factor.

Answer

True

Counterfactual is what would have happened to the same people simultaneously exposed and not exposed to the causal factor.

The Counterfactual Method

The counterfactual is what would have happened to the same people simultaneously exposed and not exposed to the causal factor.
Effect represents the difference between the two.

Causality

The counterfactual method
Criteria for causality—Lazarsfeld (1955)

1. Temporal

2. Empirical relationship

3. Relationship cannot be explained as
being caused by a third variable

Experiments or Randomized Controlled Trial Properties

Manipulation

Control

Randomization

Manipulation

Doing something to study participants
Experimenter manipulates the independent variable by administering a treatment (intervention) to some subjects and withholding it from others, or by administering some other treatment.

Control Group

Researchers can expose the control group to various conditions:

– No treatment

– Alternative treatment

– Placebo

– Standard treatment

– Different doses of the treatment

– Wait list

Randomization (Random Assignment or Random Allocation)

Involves placing subjects into treatment conditions at random
Approximates the ideal—but impossible—counterfactual of having the same people in multiple treatment groups simultaneously
Basic randomization

Question

Tell whether the following statement is true or false:

Some studies involve patient-centered interventions that are tailored to meet individual needs or characteristics.

Answer

True

Everyone in the experimental group usually gets the same intervention as delineated in formal protocols, but some studies involve patient-centered interventions (PCIs) that are tailored to meet individual needs or characteristics.

Small Table of Random Digits

Example of Random Assignment Procedure

Stratification

Divided into groups before randomized
Permuted block randomization

Blinding

Single-blind studies
Double-blind studies

Randomization

Cluster
Partially randomized patient preference design
Randomized consent design

Experimental Designs

After-only (posttest-only) design
Before–after (pretest–posttest) design
Factorial design
Crossover (repeated measures) design

Symbolic Representation of a Pretest–Posttest Experimental Design

R O1 X O2

R O1 O2

R = Randomization

O = An observation or measurement

X = An intervention

Factorial Designs

Two or more variables are manipulated simultaneously.
Test both main effects and interaction effects
Randomized block design
Crossover design

Quasi-Experimental and
Preexperimental Designs

Nonequivalent control group pretest–posttest design (quasi-experimental)
O1 X O2
O1 O2

Nonequivalent control group posttest-only design (preexperimental)
X O1
O1
One group pretest-posttest design (preexperimental)
O1 X O2

Quasi-Experimental Designs

Time series design
Nonequivalent control group before–after

design

Time Series Design

O1 O2 O3 O4 X O5 O6 O7 O8

Other Quasi-Experimental Designs

Quasi-experimental dose-response analysis
Quasi-experimental (nonrandomized) arms of a PRPP randomization design

Nonexperimental/Observational Research

Descriptive research
Correlational studies

Designs of Correlational Studies

Retrospective (case-control) design
Prospective (cohort) designs
Natural experiments
Path analytic studies

Descriptive Studies

Prevalence studies
Incidence studies