Question 1 of 1Hard
| Crowd feature | Before obstacle | After obstacle | Overall |
|---|---|---|---|
| Density | 0.8592 | 0.7308 | 0.7447 |
| Velocity |
Researcher Xiaolu Jia and colleagues monitored individuals’ velocity and the surrounding crowd density as a group of study participants walked through a space and navigated around an obstacle. Participants rated how congested it seemed before the obstacle, after the obstacle, and overall, and the researchers correlated those ratings with velocity and density. (Correlations range from to 1, with greater distance from 0 indicating greater strength). The researchers concluded that the correlations with velocity are stronger than those with density.
Which choice best describes data from the table that support the researchers’ conclusion?
- The correlation between congestion ratings before the obstacle and density is further from 0 than the correlation between overall congestion rating and velocity is.
- The correlation between congestion ratings before the obstacle and velocity is further from 0 than the correlation between congestion overall and velocity is.
- For each of the three ratings, the correlation with velocity is negative while the correlation with density is positive.
- For each of the three ratings, correlations with velocity are further from 0 than correlations with density are.
Show answer and solution
Correct answerD. For each of the three ratings, correlations with velocity are further from 0 than correlations with density are.
Solution walkthrough
- Choice D is the best answer.
- The text tells us that the farther the correlation is from 0, the “stronger” it is (doesn’t matter if it’s negative or positive).
- The table shows that the correlations with velocity are farther from zero than the correlations with density, which supports the conclusion that the correlations with velocity are stronger.
Why the other choices miss
Choice A is incorrect. This choice doesn’t support the conclusion. It makes an “apples to oranges” comparison by comparing density and velocity correlations across features instead of comparing them for each feature. Choice B is incorrect. This choice doesn’t support the conclusion. It doesn’t include the density correlations for comparison. Choice C is incorrect. This choice doesn’t support the conclusion. The text tells us that the farther the correlation is from 0, the “stronger” it is: it doesn’t matter for “strength” whether it’s negative or positive.