Why it matters
Survivorship bias inflates everything
Roughly two out of three US stocks that traded since the late nineties are gone today — bankrupt, acquired, delisted. Backtest on the survivors only, and every buy-the-dip strategy looks brilliant, because the companies that dipped and died aren't in your data. With the dead included, the numbers tell the truth.
Data hygiene
Quality control, built in
Real-world stock data is messy: recycled tickers, broken adjusted series, reverse-split artifacts that make a $2 stock look like it traded at a million. AniQuant detects them automatically and flags them — never silently hides them — so an artifact never becomes your "best strategy".