# Filtration

*Quant & Pricing — Finicade finance glossary*

A filtration is the formal record of what is known at each point in time — the mathematical object that stops a model from cheating with future information. Every conditional expectation in derivatives pricing is conditioned on one. It is what makes 'a martingale has zero expected change given everything known so far' a precise statement rather than an intuition, and what rules out look-ahead bias in a backtest.

**Also known as:** information set, filtered probability space

**Related terms:** [Martingale](https://finicade.com/glossary/martingale), [Stochastic Process](https://finicade.com/glossary/stochastic-process), [Markov Property](https://finicade.com/glossary/markov-property), [Risk-Neutral Pricing](https://finicade.com/glossary/risk-neutral-pricing), [Brownian Motion](https://finicade.com/glossary/brownian-motion)

Source: https://finicade.com/glossary/filtration