Lookahead Bias in Daily and Minute Bar Data
Summary
A forum exchange explains when bar data can introduce lookahead bias in a trading strategy. The question concerns whether a bar's closing price is available at the time a daily strategy makes its decision. The response says that, in daily strategies, using that day's high, low, close, average price, volume, or turnover amounts to using future data and should be avoided. It contrasts this with minute-frequency strategies, where orders are matched at the start of the next bar, so the described data is not considered future data in that setup.
The evidence is a brief community explanation rather than a formal platform specification or tested example. The discussion does not detail how bar timestamps, decision timing, or execution simulation are configured, all of which can affect whether a value is actually available to a strategy. Treat the guidance as a warning to align each feature with its real availability and the simulator's matching rules, and verify those rules for the specific platform and strategy frequency.
Key ideas
- Daily strategies can incur lookahead bias by using price and volume information from the same day's bar.
- The post specifically cautions against daily use of high, low, close, average price, volume, and turnover.
- It says minute strategies avoid this issue under the described convention of matching orders at the next bar's start.
- Feature availability depends on decision timing and the simulator's bar matching rules.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.