What is the test for reasonableness in the context of a judicial review of a decision made by an administrative tribunal?

The case of Dunsmuir v. New Brunswick, 2008 SCC 9 (S.C.C.), at para. 47 held that: …certain questions that come before administrative tribunals do not lend themselves to one specific, particular result. Instead, they may give rise to a number of possible, reasonable conclusions. Tribunals have a margin of appreciation within the range of acceptable and rational solutions. A court conducting a review of reasonableness inquiries into the qualities that make a decision reasonable referring both to the process of articulating the reasons and to outcomes. In judicial review, reasonableness is concerned mostly with the decision-making process. But it is also concerned with whether the decision falls within a range of possible, acceptable outcomes which are defensible in respect of the facts and law.