11 Questions
What is the primary purpose of an experimental design?
To test a hypothesis and draw causal inferences
Which type of experimental design lacks random assignment of participants to groups?
Quasi-Experimental Design
What is the function of the control group in an experiment?
To provide a baseline for comparison
What is selection bias, and how can it be addressed?
A threat to internal validity, addressed through random assignment
What is the independent variable in an experiment?
The variable being manipulated or changed by the researcher
What is the primary difference between a true experimental design and a quasi-experimental design?
The use of random assignment
What is the primary concern addressed by randomization in experimental design?
Reducing confounding variables and bias
What is the purpose of having a large sample size in experimental design?
To increase the power and precision of the study
What is the primary goal of blinding in experimental design?
To prevent participants and researchers from knowing group assignments
What is the primary concern addressed by control groups in experimental design?
External events affecting the outcome
What is the primary goal of standardized measures in experimental design?
To ensure the measurement tool remains consistent over time
Study Notes
Experimental Design in Practical Research
Definition
- Experimental design refers to the plan and structure of an experiment, including the methods and procedures used to test a hypothesis.
Types of Experimental Designs
-
True Experimental Design:
- Involves random assignment of participants to treatment or control groups.
- Allows for causal inferences about the effect of the independent variable on the dependent variable.
-
Quasi-Experimental Design:
- Lacks random assignment of participants to groups.
- Can still establish causal relationships, but with limitations.
-
Pre-Experimental Design:
- Lacks a control group or random assignment.
- Often used in exploratory or pilot studies.
Key Components of Experimental Design
-
Independent Variable (IV):
- The variable being manipulated or changed by the researcher.
- Affects the dependent variable.
-
Dependent Variable (DV):
- The variable being measured or observed.
- Affected by the independent variable.
-
Control Group:
- A group that does not receive the treatment or intervention.
- Provides a baseline for comparison.
-
Treatment Group:
- A group that receives the treatment or intervention.
- Compares to the control group to measure the effect of the IV.
Threats to Internal Validity
-
Selection Bias:
- Occurs when the groups are not comparable at the outset.
- Can be addressed through random assignment.
-
Maturation:
- Occurs when participants change naturally over time.
- Can be addressed through control groups and longitudinal designs.
-
History:
- Occurs when external events affect the outcome.
- Can be addressed through control groups and statistical controls.
-
Testing:
- Occurs when the measurement tool affects the outcome.
- Can be addressed through multiple measures and controls.
-
Instrumentation:
- Occurs when the measurement tool changes over time.
- Can be addressed through standardized measures and controls.
Experimental Design Considerations
-
Sample Size:
- Affects the power and precision of the study.
- Should be determined based on the research question and population.
-
Randomization:
- Ensures that groups are comparable at the outset.
- Reduces confounding variables and bias.
-
Blinding:
- Prevents participants and researchers from knowing group assignments.
- Reduces bias and placebo effects.
Understand the concepts of experimental design, types of designs, key components, threats to internal validity, and considerations in research. Learn about true experimental, quasi-experimental, and pre-experimental designs, and how to control for bias and confounding variables.
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