Definition
Decision quality is the property of a decision that is independent of its outcome. A high-quality decision uses the best information available, considers the relevant alternatives, weighs second-order effects honestly, and commits cleanly — even if the eventual outcome happens to be bad. A low-quality decision is one that skipped these steps, even if it happened to work.
Parrish leans heavily on Annie Duke's distinction between decision quality and outcome quality. Confusing the two — judging a decision by what happened afterwards — is what Duke calls 'resulting', and it is one of the most expensive errors in self-evaluation.
The distinction worth marking: outcomes are partly luck. Decision quality is fully yours. The first is not actionable; the second is.
Why it matters
How to evaluate
When reviewing a decision, ask three questions separately. Was the process good? — were alternatives considered, information gathered, second-order effects examined, predictions written? Was the information used well? — given what was knowable at the time, was the reasoning sound? What was the outcome? — and how much of it was luck versus the decision itself?
Only after answering the first two can the third be interpreted. Skipping straight to the outcome is the resulting trap.