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trading on forex news, interactive brokers / idealpro, and slippage
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slippage is tied to volatility, so when volatility increases the spread will also increase. there is no perfect formula to figure out slippage but from observations, it might make sense to look at the bar size in relation to previous bars to determine slippage (assuming fixed periods). this is because when there is a sudden spike in price, it's usually due to stop order triggering or a news event and those will increase the volatility dramatically in seconds.
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