December 1st, 2010, 1:48 pm
QuoteOriginally posted by: hli7at the 1min interval, are the time series dominated by noise, bid-ask bounce, or by the "real" prices?At ultra high frequency, information is dominated by the minimum price increment. Especially in equities, your new information will be mostly ticks at the bid and ask. And you will get some cancellation and placement of visible limit orders.But these are real prices. In theory, the bid will take the same amount of time to move 1 cent whether it is the minimum increment, or there are smaller increments. So in theory, you can just call this amount of time it takes the bid to move the minimum sampling interval, and sample the same pattern even if at irregular increments.The minimum increment is more of a barrier to making money than to prediction. If you buy at the offer and sell at the bid, your prediction has to be bigger than the minimum increment to make money. If you enter or exit with a limit order, you will get in and much more slowly, and so your minimum frequency has become much longer. In either case you can make predictions in a trading increment-dominated environment, but have a hard time profiting from them. If the increments were smaller, attempts to capture the correlation would fill it with noise, and your predictions would not be any better.So with big trading increments you can see correlation but you can't catch it. With smaller trading increments, the efforts of traders to catch what they see fills the ticker with noise, so that your inputs and your comprehension of the action are not automatically better.