What is the legal test for determining whether a question of mixed fact and law is correct or palpable and overriding error?

In Canada, an appeal court reviews a question of law on a standard of correctness, and a question of fact on a more deferential palpable and overriding error standard, Housen v. Nikolaisen, 2002 SCC 33, [2002] 2 S.C.R. 235 (”Housen”). An appellate court reviews a question of mixed fact and law on a standard of palpable and overriding error: Housen at paras. 26-36. A question of mixed fact and law with an extricable error in principle can be characterized as an error of law. An extricable error in principle is one that “can be attributed to the application of an incorrect standard, a failure to consider a required element of a legal test, or a similar error in principle”: Housen at para. 36.