Such a test can offer a second chance to close a short position or initiate a long. The distance from the resistance breakout to trough lows can be added on top of the resistance break to estimate a target. This would imply that the bigger the formation is, the larger the potential advance. It is important to remember that the double bottom is an intermediate to long-term reversal pattern that will not form in a few days. Even though formation in a few weeks is possible, it is preferable to have at least 4 weeks between lows.
Bottoms usually take longer than tops to form and patience can often be a virtue.
Give the pattern time to develop and look for the proper clues. Just as with the double top, it is paramount to wait for the resistance breakout. The formation is not complete until the previous reaction high is taken out. After trending lower for almost a year, PFE formed a double bottom and broke resistance with an expansion in volume. After a short pullback, there was another attempt to break above resistance, but this failed.