Study on the flyACTMathematicsData collection methods and study design
Practice 40 Data collection methods and study design questions in the app
Data collection methods and study design on the ACT Mathematics test covers how studies are set up, especially confounding and random assignment, and what those choices let you conclude.
Students must spot when a treatment is mixed with another factor, such as a work shift changing along with a training program, and explain why randomly assigning similar units to treatments, like seedlings to light conditions or plots to fertilizers, makes groups comparable.
Items typically give a short study and ask which factor is confounded or why randomization strengthens a comparison. Choices often confuse random assignment with random sampling or treat randomization as a guarantee of identical results.
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Question 1Easier
Marcus measures soil quality in 72 greenhouse plots, then randomly assigns fertilizer A or B. Which of the following best explains why the fertilizers are assigned at random?
Answer: C — It tends to balance soil quality between the fertilizer groups.
Random assignment tends to distribute soil quality and other lurking factors across the fertilizer groups. This makes the groups more comparable before outcomes are measured.
Question 2Easier
Anika randomly assigns 120 similar seedlings to either constant light or alternating light and darkness. Why does random assignment strengthen a comparison of their growth after 4 weeks?
Answer: C — It tends to balance other growth-related variables between groups
Random assignment tends to distribute lurking variables, such as initial health, across treatment groups. This makes a difference in growth more plausibly attributable to the light condition.
Question 3Easier
At a factory, morning-shift workers receive a new training program, and evening-shift workers receive the old training program. The morning group produces 14 more units per day. Which of the following factors is confounded with the training program?
Answer: B — Work shift
Every worker receiving the new program is on the morning shift, and every worker receiving the old program is on the evening shift. The effects of shift and training cannot be separated.
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Practice 40 Data collection methods and study design questions in the app
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