This is the default standard applied to most informal agency action reviewed under the APA. It is deferential — a court does not substitute its own policy judgment for the agency's — but it is not toothless; the agency must show it engaged in reasoned decisionmaking and adequately explained the path from the evidence to its conclusion.

Courts commonly evaluate the standard through a cluster of factors: did the agency consider the relevant data and articulate a rational connection between the facts found and the choice made, did it fail to consider an important aspect of the problem, did it offer an explanation that contradicts the evidence before it, and did it change position without acknowledging the change and explaining why. A reviewing court generally cannot supply a reasoned basis the agency itself did not give, which makes the adequacy of the agency's own stated explanation central to the analysis.

Inside a simulation, this standard functions as a dial on how much benefit of the doubt the agency's reasoning receives — sweeping from a highly deferential read to a searching one shows how the same administrative record can support meaningfully different projected likelihoods of the action being set aside, always presented as a modeled range rather than a prediction of any specific court's ruling.

Litigants challenging agency action under this standard build their argument around specific, documented gaps in the agency's stated reasoning — factors ignored, evidence contradicted, or unexplained departures from prior policy — since success typically turns on exposing a defect in the agency's own explanation rather than simply disagreeing with its conclusion.