Podcast
Questions and Answers
What is the primary focus of internal validity in an experiment?
Which of the following is NOT considered a threat to internal validity?
What does external validity refer to in the context of research?
In a study comparing two educational methods, which approach helps in minimizing differences between groups?
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Which of the following methods can help control for extraneous variables?
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What is a potential risk associated with participant selection that threatens internal validity?
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What is the effect of a demand characteristic on a study?
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What is a true-experimental design characterized by?
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What is the primary purpose of using a control group in true experimental designs?
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What distinguishes random selection from random assignment in an RCT?
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In a Solomon design, what is the unique characteristic of Group 3?
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What challenge is commonly faced in straight RCTs?
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Which of the following best describes the manipulation in an experimental design?
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What is the purpose of including a pre-test in an RCT?
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Which design creates a 2 x 2 model with one control and one treatment group?
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What is essential to ensure when collecting data in an experimental design?
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Study Notes
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
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Description
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.
