AP Stats Stats: Evaluation Content and Structure 3

Question 1

A researcher wants to ensure representation from each grade level in a school survey. Which method should they use?

Accepted Answer

Stratified random sample by grade level

Answer

Stratified sampling divides the population into subgroups and randomly samples from each, ensuring all strata are represented.

Question 2

An experiment uses a placebo control group. The primary purpose of the placebo is to:

Accepted Answer

Control for the psychological effect of receiving a treatment

Answer

A placebo controls for the psychological benefit subjects may experience simply from believing they are receiving treatment.

Question 3

Which principle of experimental design ensures that treatment groups are similar in all aspects other than the treatment itself?

Accepted Answer

Random assignment

Answer

Random assignment distributes variation among groups so that, on average, groups differ only in the treatment applied.

Question 4

A study surveys only people who respond to an online invitation. This introduces which type of bias?

Accepted Answer

Voluntary response bias

Answer

Voluntary response bias occurs when participation is self-selected, typically over-representing people with strong opinions.

Question 5

In blocking, subjects are grouped by a characteristic before random assignment. What does blocking accomplish?

Accepted Answer

It reduces variation within treatment groups by controlling a known source of variability

Answer

Blocking groups similar subjects together and randomizes within blocks, reducing the impact of a known nuisance variable.

AP Practice Test