Question 92·200 Super-Hard SAT Reading Questions·Information and Ideas
Mean Pollinator Visits per Observation Period
| Air condition | Meadow treatment | Mean visits |
|---|---|---|
| Ambient | Unmowed | 22 |
| Ambient | Mowed | 17 |
| Warmed | Unmowed | 18 |
| Warmed | Mowed | 9 |
Ecologist Lucía Moreno and her colleagues studied whether experimental warming and repeated mowing affect insect visits to flowering plants in meadow plots. Some plots were warmed continuously, some were mowed, some received both treatments, and some received neither. The researchers predicted that warming and mowing would amplify each other's effects rather than operate independently. Under an independent, additive model, the decline in visits for the combined treatment would equal the sum of the declines caused by warming alone and mowing alone. The researchers concluded that the results support their prediction.
Which choice most effectively uses data from the table to support the researchers' conclusion?
For a command-of-evidence question involving an interaction, identify the untreated baseline and calculate each treatment's separate effect. Keep reductions and resulting means distinct, compute the combined result predicted by the model described in the passage, and compare that prediction with the observed combined-treatment result.
Hints
Find the baseline
Use the plots receiving neither warming nor mowing as the point of comparison.
Calculate separate effects
Determine how much warming alone and mowing alone each changed the mean number of visits.
Keep quantities distinct
Add the two separate declines, convert that predicted decline into a predicted mean, and then compare the prediction with the observed combined-treatment mean.
Step-by-step Explanation
Identify the untreated baseline
The ambient, unmowed plots received a mean of 22 visits. This value is the baseline for calculating each treatment's effect.
Calculate the separate reductions
Mowing alone reduced visits from 22 to 17, a reduction of 5. Warming alone reduced visits from 22 to 18, a reduction of 4. If these effects were additive, their combined reduction would be 9, leaving an expected mean of 13 visits.
Compare the prediction with the result
The warmed, mowed plots received a mean of 9 visits, a reduction of 13 from the baseline. Because 13 is 4 greater than the additive reduction of 9, the treatments amplified each other's effects.