By controlling all extraneous variables and by randomly assigning people to different experimental conditions, an experimenter can achieve high

Question

BlackTom AI · Accepted Answer

Internal validity increases when extraneous variables are controlled and participants are randomly assigned, because those procedures protect causal inference.

1. Relevant knowledge points and concepts
- Internal validity: the degree to which changes in the dependent variable can be causally attributed to the independent variable rather than to confounds.
- Extraneous variables/confounds: uncontrolled factors that can provide alternative explanations for observed effects.
- Random assignment: distributing participants across conditions so individual differences and unknown influences are, on average, balanced across groups.
- External validity: generalizability of findings to other populations and settings.
- Reliability: consistency or repeatability of measurement.
- Sensitivity: the measure’s ability to detect a true effect (signal vs. noise).

2. Complete reasoning process step by step
- If extraneous variables are controlled (held constant or eliminated), competing explanations for differences between groups are reduced.
- Random assignment further minimizes systematic differences between groups on known and unknown participant characteristics, making it unlikely that group differences are due to preexisting factors.
- Together, control and random assignment isolate the independent variable as the most plausible cause of changes in the dependent variable.
- Therefore the principal methodological advantage achieved is stronger causal inference—i.e., higher internal validity.

3. Calculations
- No numeric calculations are required; the argument is conceptual and procedural.

4. Why the correct answer is correct
- Internal validity is specifically defined as confidence in causal attribution. Control of extraneous variables and random assignment are textbook techniques to maximize internal validity by removing alternative causal explanations.

5. Why other options are incorrect
- External validity: concerns how well results generalize beyond the study; random assignment and strict control can actually reduce external validity.
- Reliability: pertains to consistency of measurements, not the balancing of groups via random assignment.
- Sensitivity: concerns measurement precision; controlling variables and random assignment do not directly increase an instrument’s sensitivity.

6. Conclusion
The correct answer is Internal validity, which matches the provided answer.

By controlling all extraneous variables and by randomly assigning people to different experimental conditions, an experimenter can achieve highSingle choice

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