1: The wildflower meadow is what raised the moved hives' honey yield. · 2: Among colonies equally strong before the move, the meadow hives still out-yielded the old-site ones.
Grafton and Haas agree on the numbers in the report but split on what they mean. The columns ask you to pin the real point of disagreement and then find the one fact that would resolve it.
The disagreement column. Both beekeepers accept that the moved hives produced more honey this season, and both accept that the hives chosen for the move were the estate's strongest colonies to begin with; Haas says so and Grafton does not dispute it. What they actually divide on is whether the meadow raised the yield, or whether the moved hives simply out-produced because they were the strongest colonies before they ever reached the meadow. Grafton says the meadow did it; Haas doubts it. That is the claim they disagree about.
The arbiter column, the finding that settles it for Grafton. The doubt is that the moved hives started out stronger, and stronger colonies produce more wherever they are. The fact that would settle it for Grafton matches the two groups on that head start: among colonies that were equally strong before the move, did the meadow hives still out-yield the old-site ones? If, comparing only like-strength colonies, the meadow hives still come out ahead, then the meadow's edge is not the head start, because that head start has been equalized, and the forage is what remains. Holding pre-move strength fixed neutralizes the very advantage Haas named. That vindicates Grafton.
Watch the two pulls. The yield comparison, that the moved hives produced more honey, looks like the disagreement, but it is the shared starting point: neither beekeeper disputes that figure, so it cannot be what they argue over. And the strongest-colonies statement, that the moved hives were the best to start with, is the basis of Haas's doubt, also accepted by both, so it too is common ground rather than the disagreement. Picking either for the disagreement column mistakes agreed ground for the dispute. For the arbiter column, neither remaining fact settles anything: that the hives use the same box model, or that they were moved over one spring weekend, says nothing about whether the meadow or the colonies' head start produced the extra honey.
The discipline: the disagreement in a dialogue is the claim the speakers take opposite positions on, not the data they share, and when the doubt is that the treated group started out stronger, the finding that settles it compares only groups matched on that starting strength, here colonies equally strong before the move.
Disagreement: whether the meadow raised the yield. Settles it for Grafton: among equally strong colonies, the meadow hives still win.