February 14th, 2007, 8:08 am
QuoteOriginally posted by: Traden4AlphaI, personally, don't restrict my attention to the first moment of price movements. And I agree that the emphasis on first moments is one of the deep failings of TA. QF's tools for the second moment provide great value, although QF has its own failing where it uses distributions that that empirically invalid.What distributions you're talking about? There are different models and different distributions, some of them (gaussian) further, some of them (Levy-syle) closer to reality. It seems to me you're captive of some 40-years old basic research like Black-Scholes QuoteNo they aren't "words, words, words", they are the proper decision-theoretic perspective on claims made by TA (versus price prediction or correlation). TA does necessarily NOT claim that if f(Price)>80, then E(dPrice/dt) <0. Instead the claim is more of the form that if f(Price)<80 and you sell short at that point and you cover immediately if dPrice(t)/dt>0 and hold the short position as long as dPrice(t)/dt <0 or some other indicator provides a buy signal, then the total price drop (and total profit form shorting) will be large. The expectation for profit can be very different from the expectation for price change depending on the exit tactics used by the trader (QF provides some nice tools for thinking about stochastic systems and branching games with exit conditions). Moreover the expectation of profit for a roundtrip trading strategy based on a given indicator can be very different from the correlation structure between the indicator and future price movement. My point is that correlation between an indicator and prices is neither necessary nor sufficient for profits.Aaargh I understand your concern about correlation, ok, now could you PLEASE specify some strategy, some statement, conditional on something in the past probably, but well-defined, so we could test it? Otherwise we're just wasting time speaking about the maturity of pink elephants.QuoteThe fact that GARCH does a better job of simulating price data is intriguing to me for what it says about risk vs. return. Isn't there a bit of a paradox to persistence of volatility and non-persistence of excess rates of return? Why not consistently buy persistently volatile security to earn a higher rates of return? And if a forecast of high volatility isn't a forecast of high return, then why not avoid all high volatility securities?Very interesting remark, never thought about this. Is volatility persistent on the big timeframes (i.e. daily/weekly)? I thought it's persistent on the small timeframes like M1 - M15, so there isn't a lot of forecasting power there?QuoteThen why do so many traders still use TA? Why are TA tools built into trading platforms, data services, and Bloomberg? We could just scoff at traders' use of TA as just a case of financial astrology, but that would miss a great opportunity to learn something deeper about the markets. If a sufficient fraction of volume is driven by TA-influenced trading, then what will that do to prices?Well, it's not a bad proof, that someone uses it ergo it's good. But we don't know whether someone uses it. Yes, some trader can say: I use TA & TA is useful. But they won't share his secrets with you therefore they don't make any claims. So their theory couldn't be verified. Moreover, I don't know any sucessful trader using TA (although I don't know many succesful trader at all). Surely you can use moving average and say that you are using TA - but that would be a bit unfair. Likewise I can use moving average and say that I use regression and square-least error thus I use QA.