A study found that employees who regularly use standing desks report fewer instances of back pain compared to those who use traditional sitting desks. The study concluded that companies should invest in standing desks to reduce employee back pain. Which of the following, if true, would most seriously weaken the study's conclusion?
- ASome traditional sitting desks can be adjusted to ergonomic specifications, reducing back pain.
- BMany employees find standing desks uncomfortable and revert to sitting for most of their workday.
- CThe study only included participants from one industry, primarily office workers.
- DEmployees who choose to use standing desks are generally more health-conscious and active outside of work.
Show answer & explanationAnswer & explanation
Correct answer: D. Employees who choose to use standing desks are generally more health-conscious and active outside of work.
The study attributes reduced back pain to standing desks. To weaken this causal conclusion, one could introduce a confounding variable or self-selection bias. Option A suggests that people who *choose* standing desks are already more health-conscious. This means their lower back pain might be due to their overall healthier lifestyle, not solely the standing desk, thus weakening the claim that standing desks *cause* reduced pain.
Why the other options are wrong
- A. This suggests an alternative solution for back pain but doesn't directly weaken the claim that standing desks also reduce back pain.
- B. This highlights a practical limitation of standing desks but doesn't directly challenge whether they *can* reduce back pain if used consistently.
- C. This points to a limitation in the study's generalizability but doesn't directly weaken the causal conclusion for the population studied.
Weakening Causal Claims (Confounding Variable)
To weaken a causal claim by identifying a confounding variable means introducing a third factor that is related to both the presumed cause and effect, thereby offering an alternative explanation for the observed correlation.
- Introduces a third variable (Z).
- Z is related to both X (cause) and Y (effect).
- Z potentially explains the correlation between X and Y.
Memory trick: Is it A causes B, or B causes A, or C causes both?