AP Stats Experimental Design 3

Question 1

An experiment uses a matched pairs design where each participant is tested under both the old and new software interfaces on different days. The order of interfaces is randomized for each participant. What does randomizing the order control for?

Accepted Answer

Carryover or order effects

Answer

Randomizing order in a matched pairs design controls for carryover and order effects that could bias results.

Question 2

A clinical trial randomly assigns 500 patients to drug A and 500 to a placebo. After the trial, it is discovered that patients in the drug A group were, on average, younger. This is an example of:

Accepted Answer

Chance imbalance due to random variation

Answer

Random assignment does not guarantee perfect balance — chance variation can create group differences, especially with smaller samples.

Question 3

Which of the following best describes the principle of replication in experimental design?

Accepted Answer

Using enough experimental units per treatment to detect real effects

Answer

Replication means having multiple experimental units per treatment group so that results are reliable and not due to a single unusual unit.

Question 4

A study compares two teaching methods by having Teacher A use Method 1 and Teacher B use Method 2. The teaching method is confounded with:

Accepted Answer

The teacher (a potential lurking variable)

Answer

Because each teacher uses only one method, any observed difference could be due to the teaching method or the individual teacher.

Question 5

In an experiment testing three doses of a medication, a researcher uses a Latin square design to control for both time period and patient order effects. This is an extension of:

Accepted Answer

Blocking in two directions simultaneously

Answer

A Latin square design blocks in two directions (rows and columns) simultaneously, controlling for two sources of variation.

AP Practice Test

AP Practice Test

AP Stats Experimental Design 3