Sampling and Study Design

What a study can and cannot claim.

11 problems · about 24 minutes · AP Statistics 3.2, 3.4, 3.5

NameDate

Figure — use these to answer the problems

Two groups compared. Whether the difference means anything depends on the design.

Treatment7

Control4

Treatment7

Control4

Figure 1

Straightforward practice. Get the method working first.

4 problems

Which is required to claim causation? 1 for random sampling, 2 for random assignment.
Answer
Sort each study by what it can support.
Write each item under the heading it belongs to: Survey of volunteers · Randomised controlled experiment · Observing two existing groups
Association only
Causation
A voluntary online poll. Is it likely biased? 1 for yes, 0 for no.
Answer
Does a larger biased sample fix the bias? 1 for yes, 0 for no.
Answer

The same ideas with more to keep track of.

3 problems

A lurking variable explains an association. Was the study observational? 1 for yes, 0 for no.
Answer
6
Match each design feature to what it protects against.
Draw a line from each item on the left to its match on the right.
- Random assignment
- Control group
- Blinding
- Lurking variables
- Having nothing to compare against
- Expectations changing the result
A census surveys what fraction of the population? Give it as a decimal.
Answer

Mixed problems. Work out what kind of question it is before you start.

4 problems

Convenience sampling. Is it random? 1 for yes, 0 for no.
Answer
An experiment with random assignment but volunteer subjects. Can it claim cause? 1 for yes, 0 for no.
Answer
The Right to Generalise
Which gives the right to generalise to a population? 1 for random sampling, 2 for random assignment.
Answer
The Right to Claim Cause
Which gives the right to claim causation? 1 for random sampling, 2 for random assignment.
Answer