A graph question that asks for support tests whether the numbers show every part of a claim. Read the claim first and separate what it says about each condition. Then read the title, axes, and key to see what each bar measures. For stacked bars, add the segments to find the total, and compare both the parts and the totals. Correct numbers aren't enough if a choice's conclusion doesn't follow from them.
Hints
- Hint 1
Look at both parts of the ecologists’ proposal. What does each part say about the timing of visits and the total number of visits?
- Hint 2
Use the legend to separate daytime from nighttime visits. How do those two segments combine to give visits over the full 24-hour period?
- Hint 3
Compare each lit condition with 0 lux. Work out the daytime change, the nighttime change, and the change in their sum.
Step-by-step
Compare timing changes with total visits
Step 1Split the proposal into two tests
The proposal says moderate lighting mainly changes when visits occur without reducing overall visitation, but brighter lighting suppresses overall visitation. What must the data show? Moderate lighting needs a shift between day and night with no drop in total visits, while brighter lighting needs a lower total. Both timing and total visits matter.
- Step 2
Read the two parts of each bar
The title and axes show visits per plot at three lighting levels, and the key separates daytime from nighttime. How do we find visits over a 24-hour period? Add the two labeled segments, because each covers only part of the day. At 0 lux, with no artificial night lighting, the total is 62 + 38 = 100 visits.
- Step 3
Check the moderate lighting
Does 5 lux change timing without cutting overall visitation? Daytime visits rise from 62 to 75, a gain of 13, while nighttime visits fall from 38 to 27, a loss of 11. The changes nearly balance: 13 - 11 = 2, so the total rises from 100 to 102. The timing shifts toward daytime, but the total doesn't fall.
- Step 4
Check the brighter lighting
At 20 lux, does the daytime gain make up for the nighttime loss? Daytime visits rise by 6, from 62 to 68, but nighttime visits drop by 24, from 38 to 14. Since 6 - 24 = -18, there's a loss in total visits, not only a shift in timing. The choice with a net decrease of 18 shows brighter lighting suppresses overall visitation. Choice A.