Tick Data Versus Bar Data: Why the Same Test Gives Different Results
Posted: Sun Oct 04, 2026 12:58 pm
Tick Data Versus Bar Data: Why the Same Test Gives Different Results
When you test a strategy, the quality of price data changes the answer. Two main types exist: bar data and tick data.
Bar data, also called OHLC data, records open, high, low, and close for each period. It is compact and widely available. But it hides what happened inside each bar. If a candle's range includes both your stop and your target, a test cannot know which was hit first. Software often assumes a rule, and that rule can be optimistic.
Tick data records every price change. It allows tests to replay the actual sequence of movement, resolving the order of events inside bars. It also shows spread variation and, with good quality, realistic stop behavior.
The difference matters most for short-term strategies with tight stops and targets. For daily strategies with 100-pip stops, bar data gives reasonable results.
Tick data has its own problems. Files are large, and quality varies. Brokers' tick feeds differ, and some historical data is modeled, meaning interpolated from bars and not recorded, which can be misleading. Platforms usually label the modeling quality of a test.
If you test a scalping strategy on one-minute bars, treat the results with suspicion.
Practical step: check the data quality percentage reported in your testing platform and what kind of data it used.
When you test a strategy, the quality of price data changes the answer. Two main types exist: bar data and tick data.
Bar data, also called OHLC data, records open, high, low, and close for each period. It is compact and widely available. But it hides what happened inside each bar. If a candle's range includes both your stop and your target, a test cannot know which was hit first. Software often assumes a rule, and that rule can be optimistic.
Tick data records every price change. It allows tests to replay the actual sequence of movement, resolving the order of events inside bars. It also shows spread variation and, with good quality, realistic stop behavior.
The difference matters most for short-term strategies with tight stops and targets. For daily strategies with 100-pip stops, bar data gives reasonable results.
Tick data has its own problems. Files are large, and quality varies. Brokers' tick feeds differ, and some historical data is modeled, meaning interpolated from bars and not recorded, which can be misleading. Platforms usually label the modeling quality of a test.
If you test a scalping strategy on one-minute bars, treat the results with suspicion.
Practical step: check the data quality percentage reported in your testing platform and what kind of data it used.