Lookahead Bias Quant Interview Guide
Lookahead bias quant interview guide covering future data, revisions, release timing, feature construction, examples, and checks.
Candidates validating point-in-time features and backtests.
Lookahead bias uses future information
Lookahead bias occurs when a feature, label, universe, or backtest decision uses information unavailable at the historical decision time.
Release timing matters
Economic data, estimates, fundamentals, and vendor feeds may have publication lags or revisions that differ from their period labels.
Concrete example
Using final quarterly fundamentals on the quarter-end date leaks information if the report was published weeks later to the market.
Check every join
Use as-of timestamps, release calendars, vendor availability fields, and lagged joins that mimic what the strategy could know.
Common mistakes
Candidates often sort by date and assume safety. Date order alone does not prove the data was available at decision time.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.