FAST Experimental Design 2 — Questions and Answers
Question 1: A researcher wants to test whether a new fertilizer increases crop yield but cannot randomly assign plots to treatments because some plots are on hillsides. Which design best addresses this?
- Completely randomized design
- Randomized block design (Correct answer)
- Factorial design
- Crossover design
Correct answer: Randomized block design
A randomized block design groups plots by location type (hillside vs. flat) to control for terrain as a confounding variable.
Question 2: In a double-blind drug trial, which of the following best describes what 'double-blind' means?
- Both the drug and placebo are tested simultaneously
- Neither the participants nor the researchers assessing outcomes know who received the treatment (Correct answer)
- Two different drugs are compared against each other
- The study is conducted at two separate research sites
Correct answer: Neither the participants nor the researchers assessing outcomes know who received the treatment
Double-blind means both participants and outcome assessors are unaware of group assignments to prevent bias.
Question 3: A study finds that cities with more ice cream sales have higher drowning rates. What is the most likely explanation?
- Ice cream consumption causes drowning
- Drowning increases demand for ice cream
- A third variable (hot weather) drives both (Correct answer)
- The data was collected incorrectly
Correct answer: A third variable (hot weather) drives both
Hot weather causes both increased ice cream consumption and increased swimming, making temperature a confounding variable.
Question 4: Which of the following is an example of a within-subjects experimental design?
- Randomly assigning participants to either a treatment or control group
- Having each participant complete all conditions of the experiment (Correct answer)
- Matching participants by age before assigning them to groups
- Using historical data as a comparison group
Correct answer: Having each participant complete all conditions of the experiment
A within-subjects design has each participant experience all conditions, serving as their own control.
Question 5: A researcher tests five different teaching methods but only has access to five intact classrooms. What is the primary limitation of this setup?
- Too few teaching methods were tested
- Students cannot be randomly assigned to classrooms, limiting causal inference (Correct answer)
- The study lacks a control group
- Five classrooms is too small a sample for any analysis
Correct answer: Students cannot be randomly assigned to classrooms, limiting causal inference
Using intact groups rather than random assignment creates a quasi-experimental design, weakening causal conclusions due to potential pre-existing group differences.
Question 6: What is the purpose of including a control group in an experiment?
- To ensure all participants receive some benefit
- To provide a baseline comparison that isolates the effect of the independent variable (Correct answer)
- To double the sample size for statistical power
- To test a second independent variable simultaneously
Correct answer: To provide a baseline comparison that isolates the effect of the independent variable
A control group establishes a baseline against which the treatment group is compared, allowing the effect of the independent variable to be isolated.
Question 7: An experiment uses a 2×3 factorial design. How many total conditions does this experiment have?
- 2
- 3
- 5
- 6 (Correct answer)
Correct answer: 6
A 2×3 factorial design has 2 levels of one factor and 3 levels of another, yielding 2×3 = 6 unique combinations.
FAST Experimental Design 2
A researcher wants to test whether a new fertilizer increases crop yield but cannot randomly assign plots to treatments because some plots are on hillsides.
Which design best addresses this?