True Experimental Designs

True Experimental Designs

• Often referred to as Randomized Controlled Trials (RCTs)
• Follow these principles:
  • Random selection from a population (chance of being selected)
  • Random assignment within the sample (equal opportunity for control or experimental groups)
  • Use of a control group (often receives 'no treatment')
  • Manipulation (the treatment is applied to the experimental group)

Using a Control Group

• Crucial for determining if an effect is present
• The control group typically receives no treatment

Experimental Group

• Receives the treatment
• Simple model: 1 control group, 1 treatment group (creating a 2x2 model)
• More complex: 1 control group, multiple treatment groups

Including a Pre-test

• Important to assess if groups are equal before the intervention
• In RCTs, groups are randomly selected and assigned, making a pre-test unnecessary

Practical View of an RCT (Example)

• Recruitment and screening
• Baseline assessment
• Randomization to intervention or control groups
• Intervention group: receives educational material on Alzheimer's disease, physical activity workshop, and telephone monitoring
• Control group: receives usual care and telephone calls
• 6-month assessment
• 12-month assessment
• Baseline surveys, follow-up surveys (four rounds)
• WASH program (WaterAid)
• Mass Chemotherapy with Albendazole

Cross-Over Designs

• Group A receives Condition 1, then Condition 2
• Group B receives Condition 2, then Condition 1

Solomon Designs

• Uses a control group with and without a pre-test
• Experimental groups with and without a pre-test

RCTs (General Points)

• Straight RCTs are most commonly used
• Main difficulty is implementation and lack of time
• Most studies use an OXOX method for treatment control

Validity in Experimental Designs

• Validity ensures the treatment/test/intervention achieves its intended purpose
• Experiments need validity to be considered relevant
• Different types of validity exist, important for study design

Internal & External Validity

• Internal validity: degree of control over the experiment; extraneous variables impacting results
• External validity: how generalizable the results are to other settings
• Threat management and control are crucial but possibly at a trade-off, depending on circumstances

Threats to Internal Validity

• Participant selection
• Practice effects
• Regression to the mean
• Instrumentation (subjectivity in scoring)
• Mortality (loss of participants)
• Maturation (physical or psychological changes over time)

Threats to External Validity

• Effect of pre-test
• Demand characteristics
• Experimenter effects

Controlling External Validity Threats

• Matching groups
• Finding similar groups to minimize differences
• Using techniques to control extraneous variables

Summary So Far

• Research generally builds an argument through literature review
• Several research designs explored, such as descriptive, correlational, quasi-experimental, and true-experimental designs
• Pros and cons of each design and their effect on results should be considered

Explore the principles of true experimental designs, including Randomized Controlled Trials (RCTs). This quiz will test your understanding of control groups, experimental groups, and the importance of random selection and assignment. Enhance your knowledge of how these designs facilitate accurate research outcomes.