AP Statistics · Topic 3.5
Introduction to Experimental Design Practice
Part of Collecting Data.(VAR-3.A)
Practice questions
31
Sample questions
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Sample 1difficulty 1/5
A researcher tests a new battery design by giving the new battery to one device and the old battery to another device, then measuring runtimes once each.
Which principle of experimental design is most violated?
- Acheck_circle
Replication
- B
Blinding
- C
Blocking
- D
Random assignment
Why
With only one observation per treatment, there is no way to estimate variability or confirm the effect. Replication (multiple experimental units per treatment) is essential.
- A
Sample 2difficulty 1/5
In a study comparing two fertilizers on tomato yield, 30 garden plots are randomly assigned to receive one of the two fertilizers.
What are the experimental units?
- A
The gardener
- B
The two fertilizers
- Ccheck_circle
The 30 garden plots
- D
Tomato yield
Why
Experimental units are the entities to which treatments are randomly assigned. Here, the plots receive the treatments.
- A
Sample 3difficulty 1/5
A study tests three doses of a drug (low, medium, high) plus a placebo.
How many treatments does this experiment have?
- A
2
- B
3
- Ccheck_circle
4
- D
1
Why
Three drug doses plus one placebo gives four treatment groups.
- A
Sample 4difficulty 1/5
In a clinical trial for a new pain reliever, half of the volunteers receive the actual drug and the other half receive a sugar pill that is identical in appearance but has no active ingredient. Neither volunteers nor the doctors evaluating them know which pill each volunteer received.
What is the primary purpose of giving the sugar pill (placebo)?
- A
To save money on the experiment
- Bcheck_circle
To create a control group whose response can be compared with the treatment group
- C
To increase the sample size
- D
To reduce variability among subjects
Why
A placebo creates a control group that is treated identically except for the active ingredient, allowing the researcher to attribute differences in response to the drug rather than to the act of taking a pill.
- A
Sample 5difficulty 1/5
In the trial above, neither the patients nor the doctors recording outcomes know who received the active drug versus the placebo.
This experimental feature is called
- A
Stratification
- B
Single-blinding
- Ccheck_circle
Double-blinding
- D
Random assignment
Why
A double-blind experiment prevents both subjects and evaluators from knowing the treatment assignment, eliminating bias from expectation effects on either side.
- A