Rolling an 11 or higher on a d20 is a 50% chance, not a 45% one. 11-20 = 10 results 1-10 = 10 results
Caster Level[]
This entire page is based around checks vs. Dispels depending on Caster Level. However, in fact every spell, including those from items (wands, scrolls, etc.), are cast at Character level vs. Dispels. This bug has existed and has been experienced by players since the early stages of the game, however it opened itself to misinterpretation in the past. Caster Level still applies for durations, SR and spell effects.
A few sources, amongst others: (1), (2), (3), (4), (5), (6)(talk) 19:11, November 13, 2012 (UTC)