Experiments and Observational Studies

Only one of them can prove a cause.

12 problems · about 21 minutes · TEKS P.S.4.B, S-IC.B.3

NameDate

Figure — use these to answer the problems

Treatment against control. The gap between them is the evidence, and it means nothing without the control bar.

Treatment14

Control8

Treatment improved14

Control improved8

Figure 1

Straightforward practice. Get the method working first.

5 problems

Subjects are randomly assigned to two diets. Experiment or observational? 1 or 2.
Answer
2
Why does random assignment allow a causal conclusion?
- It balances out other differences between the groups.
- It feels fairer to the subjects.
Which design can establish causation? 1 experiment, 2 observational.
Answer
A group receiving a fake treatment is called what? 1 control, 2 treatment.
Answer
Neither subjects nor measurers know the groups. Double blind? 1 yes, 0 no.
Answer

The same ideas with more to keep track of.

3 problems

Subjects improve from believing they were treated. Placebo effect? 1 yes, 0 no.
Answer
Students choose their own study method. Experiment or observational? 1 or 2.
Answer
What balances out unknown differences between groups? 1 random assignment, 2 a large sample.
Answer

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

4 problems

Sort each feature by which design it belongs to.
Write each item under the heading it belongs to: Random assignment to groups · A placebo control group · Recording choices people already made · Following existing habits over time
Experiment
Observational study
Can an observational study alone prove cause? 1 yes, 0 no.
Answer
The Design
Researchers randomly assign a drug or a placebo. Experiment or observational? 1 experiment, 2 observational.
Answer
The Watch
Researchers record existing exercise habits and compare health. Which is it? 1 or 2.
Answer