Question 53·Medium·Evaluate Statistical Claims: Observational Studies and Experiments
A researcher wants to investigate whether using a standing desk improves students’ ability to concentrate. An announcement is posted at a university asking for volunteers, and 60 students respond. The researcher randomly assigns 30 of the volunteers to use standing desks during a 50-minute study session and 30 to use traditional seated desks. After the session, each student takes a concentration test, and the standing-desk group scores significantly higher than the seated-desk group.
Which conclusion is most supported by the design of this study?
For questions about study conclusions, first identify the design: look for key words like "randomly assigned" (experiment, allows causation) versus "surveyed," "observed," or "chose" (observational, no causation). Next, check who the participants are and how they were selected to see how far you can generalize (only to similar volunteers, to the whole school, or more broadly). Finally, pick the answer that matches both the strength of conclusion allowed (causal vs. associative) and the scope (only participants in this study vs. a wider population), and eliminate options that are either too strong or too broad.
Hints
Look at how participants were assigned to groups
Focus on the sentence that says how the 60 students were split into standing-desk and seated-desk groups. Ask: Were they just observed, or were they randomly assigned?
Think about causation vs. association
Once you know whether this is an experiment or an observational study, decide if it is appropriate to make a causal claim (that one thing causes another) or only a correlational claim (they are just related).
Consider who the results can represent
The students in the study were volunteers from one university doing a single 50‑minute session. Ask: Is it safe to extend the conclusion to all students at that university, or even all college students?
Match scope and strength of claim
Eliminate choices that either (a) go beyond the specific group and setting of the study, or (b) refuse to make a causal statement even though the design allows it.
Step-by-step Explanation
Identify the type of study
Read how the study was done: 60 students volunteered, and then the researcher randomly assigns 30 to standing desks and 30 to seated desks. Random assignment of subjects to treatments makes this a randomized experiment, not just an observational study.
Decide if causation is allowed
In a randomized experiment, random assignment tends to balance other factors (like prior concentration ability, sleep, etc.) between groups. That means a difference in average test scores between groups can reasonably be attributed to the treatment (standing vs. sitting) for the people in the experiment. So a causal conclusion is allowed within this study.
Decide how far we can generalize
Notice that the participants are volunteers, not a random sample of all students at the university or of all college students. Also, the test is after one 50‑minute study session, not over many sessions or semesters. This limits how far we can generalize: we should not claim results for all university students or all college students, only for the volunteers under these specific conditions.
Match the strongest justified conclusion to an answer choice
We need the choice that (1) allows causation and (2) keeps the claim restricted to the volunteers in this study and this particular session. That is exactly what "Using a standing desk causes the volunteers in this study to concentrate better during the particular session." states, so this is the most supported conclusion.