You really don't know what you are talking. As long as you follow the TOS you are OK even with 20% or more.
The CTR depends on your site content, the ad placement, colors, etc - there are many factors to this. May we see your site URL, to try to help you see why it's so high?
It depends on from who you have heard that... probably not reliable source. Having CTR 10 - 15% is nothing strange or weird.
Why are so many people asking about their CTR??? Who cares what your CTR is!!! If you're not doing click fraud or going against the Adsense TOS there is no reason to worry.
High CTR is nothing to worry about as long as you're not breaking TOS. I've consistently run CTRs from the mid-20% to low 30% range for over a year with no problems. Lots of people have numbers higher than that. However, if you break the TOS, you will have a lot to worry about.
Nonsense, nonsense. The blind leading the blind. I have had 16%+ average for one entire site for three years. Some individual pages are consistently 50%+. CTR has nothing to do with being banned. It's *how* the CTR is achieved that can get you banned. If your high CTR is a result of someone suddenly and maliciously clicking on multiple ads, multiple times, on a page or two, that's a problem.
Don't worry about CTR as long as you're not breaking adsense TOS. some web have CTR > 40% . CTR's upto your content and ad position, color and many thing.