idealist.org

One of the best ways to validate a forex technical indicator is volume. When volume is strong, indicators tend to be more accurate. Unfortunately, there is no volume data available for the forex markets. Using trading ranges is the next best thing. Having this data in hand, the trader can more carefully evaluate when to trade. Not only will technical indicators generally have more accuracy at different points of the day, but there is both more profit potential and less loss potential at other times of the day. Consider a trade in EURUSD at 10 AM EST vs. one at 10 PM EST. The first has an average trading range of 30 pips, the second, 10 pips. Entering the market during the morning trade creates some interesting possibilities – the market may go against you or with you, but you should be prepared for a ride in either case. On the other hand, if the market goes against you 10 pips at 10 PM, how concerned should you be? Probably not as much as if it was 4 AM.

... source http://www.trader-info.org