A finding question about several groups tests whether a result backs up the exact prediction, not only its topic. Start with the prediction and put it in a few words, naming what changes, what should happen, and to whom. Then ask which groups or treatments it compares, and predict the needed result. A claim with several parts needs evidence for every part, using the same comparisons. Findings can sound relevant while measuring something the prediction doesn't say.
Hints
- Hint 1
In the final sentence, look for what links the microbes to the seedlings. Put that prediction in a few words.
- Hint 2
Work out a separate comparison for each grass species. What does especially ask you to show in each comparison?
Step-by-step
Test both treatment comparisons
Step 1Put the prediction in a few words
Okafor expects a special benefit for the species from whose roots that community had been collected. What does that prediction say in a few words? Microbes should help most when their source species matches the seedlings, so a supporting finding must test that matching benefit for both grasses.
- Step 2
Predict the two comparisons
What does especially ask us to compare? Let's compare the two microbial sources within each seedling species. Predict beachgrass growing more with beachgrass-root microbes than with panicgrass-root microbes, and panicgrass growing more with panicgrass-root microbes than with beachgrass-root microbes. Each grass should do better with its own root microbes than with the other grass's microbes. Growth above the uninoculated control alone tells us microbes help, but not whether matching the source gives the special benefit.
- Step 3
Set aside findings that miss a part
Do the findings test that benefit for each microbial community? The finding that puts beachgrass-root microbes ahead for both grasses misses panicgrass's predicted advantage with its own microbes. With unmeasured cross-species treatments, we can't compare either grass's growth across microbial sources. And microbes that differed in composition aren't evidence that each source helped its own grass more. Those findings don't show the matching benefit for both grasses.
- Step 4
Read the reverse pattern
The reverse pattern tells us panicgrass produces more biomass with panicgrass-root microbes than with beachgrass-root microbes. Beachgrass also does better with its own root microbes, so the better source switches with the seedling species. That matches the prediction for the species from whose roots that community had been collected. Choice B.