Quote from nononsense:
In fact a poster pointed out that a good measure of trendiness is for him the profitability of his trading strategy. This is probably the only sensible approach but is at the same time very subjective. It has only meaning for the trader familiar with his own strategy.
The threads about random trading started me thinking about this. It would be possible to define trendiness in terms of the profitability of random entry trading with fixed target and stops. It is easy to see that a in a strongly trending market, the win/loss rate of random entry, fixed stop/target trading will approach 50% even with a profit/loss ratio greater than 100%, resulting in a positive expectancy. (50% of the time the random entry will put you in the right direction).
This definition of trendiness would be dependent on the size of the moves targeted, so with a little thought it should be possible to create an indicator which takes three parameters - a stop, a target, and time frame. The indicator would look back at the price action over the desired time frame, and give a result based on the probability of hitting the target before hitting the stop, assuming a random entry time and direction.
It could be normalized so that 100% represents maximum trendiness (50% win/loss rate of random entry), 50% represents a random market [causes the random entry system to break even -> win/loss rate = loss/(profit+loss)], and approaching 0% means the market is much choppier than random for the size moves you are targetting and you are better off with a wide stop and a tight target.

) - in real 9254 for that session (the day Saddam was captured the model seems to project before it was known publicly