I think 3% CTR is good. I have a low ctr [less than 1%]. Anyway, some people even have 10% or more CTR. You can increase your CTR, via placing the ads in the right place.
As santosh said, CTR can vary for many reasons. I have a few pages on my sites that consistently get high double-digit CTRS, and others that consistently get very low CTRs, lower than 3%. What's the difference? In general, visitors to the pages with high CTR are hungry for information on the topic of the page, and my pages don't give them nearly enough to satisfy their needs. Therefore, they click ads that are relevant to the topic and that promise more information. Visitors to the pages with low CTRs are apparently satisfied with the information I provide and don't click ads as often. Pages about topics that have multiple answers or multiple products, and you only offer a couple of answers, will get ad clicks. Pages about topics that have only one answer, and you give that answer, will get almost no ad clicks. For example, if your page offers a download of a game that people are looking for, after they have downloaded that game, they have no reason to click on ads that are also about that game.
i have 2 accounts, Company and Individual. 1 got avg of 26~30% CTR and the second one got avg 50~70% CTR when i started i never even dreamed of 7% but practicing over and over and after 5 years i reached that. though income is still not very high