Week 3: Quantitative Study Designs

Filtered Information

Top hierarchy level including Systematic Reviews, CATs, and CAPs.

Unfiltered Information

Primary research designs including RCTs, cohort, case-control studies, and expert opinion.

Independent Variable (IV)

The manipulated condition, intervention, or predictor variable.

Dependent Variable (DV)

The measured outcome, response, or effect variable.

Operational Definition

Specifies exactly how an IV is manipulated or a DV is measured.

Experimental vs. Observational Decision

Experimental studies assign interventions; observational studies only observe natural occurrences.

Randomized Controlled Trial (RCT)

Experimental design using random assignment, manipulation, and control groups.

RCT Causal Relationship

The gold standard design capable of establishing true cause-and-effect relationships.

Three Core Characteristics of an RCT

Randomization, manipulation, and control.

Quasi-Experimental Design

Intervention study lacking random assignment or comparison groups.

Pretest-Posttest Control Group Design

Between-group design comparing baseline and post-intervention outcomes across distinct groups.

Within-Group Comparison Design

Design where subjects serve as their own control across multiple conditions.

One-Way Repeated Measures Design

Within-subject design where participants complete multiple sequential interventions.

Crossover Design

Participants receive alternative interventions sequentially over set periods.

Learning/Practice Effect

Order effect where performance improves simply from repeating a task.

Carryover Effect

Order effect where exposure to one treatment alters response to a subsequent treatment.

Wash-Out Time

Rest period between treatment conditions used to prevent carryover effects.

Descriptive Observational Studies

Studies describing data and population characteristics without explaining cause or mechanism.

Cohort Study Direction

Tracks subjects forward or backward from exposure to outcome.

Prospective Cohort Study

Starts in the present and follows exposed groups forward into the future.

Retrospective Cohort Study

Analyzes past exposure data to determine subsequent historical or current outcomes.

Case-Control Study Direction

Starts with the outcome and looks backward to assess historical exposure.

Matching in Case-Control Studies

Pairing controls with cases on specific variables to minimize confounding factors.

Cross-Sectional Study

Measures exposures and outcomes simultaneously at a single point in time.

Single-Subject Design (N=1)

Tracks individual progress using continuous baseline (A) and intervention (B) measurements.

Confounding Variable

Extraneous factor associated with exposure and outcome that distorts true relationships.

Co-Intervention

Confounding issue where participants receive outside therapies concurrently with the study treatment.

Selection Bias

Systematic error resulting from flawed sampling or group assignment processes.

Measurement Bias

Systematic error caused by flawed data collection tools or procedures.

Double-Blind Study

Design where both participants and researchers are unaware of group assignments.