Out of sample
Data not used for the design decision being evaluated. A date range labelled OOS loses that role once its results guide additional choices. Preserve access history, not just split filenames.
Drawdown and slippage
Drawdown is the decline from a prior equity high, with starting equity included. Slippage is the difference between a reference price and an actual or simulated execution; its sign convention and measurement source must be explicit.
Survivorship bias and a candidate
Survivorship bias occurs when past evaluation omits instruments that did not survive to the collection date. A research candidate is an idea requiring further verification. It is not a deployable strategy, a validated edge or a profit guarantee.