Quote from easyguru:
Here is the Brandon post
My figures are slightly different, but the gist is the same:
The average gap is just under 1.2% (on the Naz). These fill 71% of the time.
Gaps that are double that - just over 2% - fill only 36% of the time.
Gaps of 3% (6% of all gaps) fill only 23% of the time.
Gaps of 4% or more (2.4% of all gaps) fill only 5% of the time.
[My note: since the larger gaps happen so rarely, it's difficult to say how much upside is left after such a large opening gap, unless it's a Trap Gap; someone with a much deeper archive of charts than I have would have to look at this and assess the probabilities for trading in the direction of the gap, i.e., rather than fading it]
--Db