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.
AP Stats Experimental Design 1
What is the primary purpose of a control group in an experiment?