AP Stats Experimental Design 1 — Questions and Answers
Question 1: What is the primary purpose of a control group in an experiment?
- To provide a baseline for comparison against the treatment group (Correct answer)
- To increase the total sample size
- To receive the most promising treatment
- To observe natural behavior without any intervention
Correct answer: To provide a baseline for comparison against the treatment group
The control group serves as a reference point, allowing researchers to determine whether the treatment had an effect.
Question 2: What is random assignment and why is it important?
- Randomly placing participants in groups to equalize confounding variables (Correct answer)
- Randomly selecting participants from the population
- Assigning participants alphabetically
- Letting participants choose their own group
Correct answer: Randomly placing participants in groups to equalize confounding variables
Random assignment distributes known and unknown confounding variables equally across groups, strengthening causal conclusions.
Question 3: What is a confounding variable?
- A variable that influences both the independent and dependent variables (Correct answer)
- Any variable measured in the study
- The variable being manipulated
- A variable that only affects the control group
Correct answer: A variable that influences both the independent and dependent variables
Confounders create alternative explanations for results by simultaneously affecting the treatment and outcome.
Question 4: What is the difference between internal and external validity?
- Internal validity is confidence in causal conclusions; external validity is generalizability (Correct answer)
- They are the same concept
- Internal validity only matters for lab studies
- External validity is always more important
Correct answer: Internal validity is confidence in causal conclusions; external validity is generalizability
Internal validity ensures the study accurately identifies causal relationships, while external validity indicates how well results apply to other settings.
Question 5: What is a double-blind experiment?
- Neither participants nor researchers know who receives treatment or placebo (Correct answer)
- Both groups receive the treatment
- The experiment is repeated twice
- Two different treatments are tested simultaneously
Correct answer: Neither participants nor researchers know who receives treatment or placebo
Double-blinding prevents both participant and researcher expectations from influencing results, reducing bias.
Question 6: Why is replication important in experimental research?
- It confirms that findings are reliable and not due to chance or specific conditions (Correct answer)
- It is only necessary when initial results are surprising
- Replication wastes resources on redundant studies
- Only exact replications are valuable
Correct answer: It confirms that findings are reliable and not due to chance or specific conditions
Replication verifies that results are robust and generalizable, not artifacts of specific conditions or sampling variability.
