First myth about google adsense to earn more money

The first Myth what peoples talk in most of the forums is using wide ads like 336x280, 300x250 and 250x250 are more effective in many websites, it must also be doing the same thing in my website. Is it true that people who are using the above mentioned ads are earning more money in google. Not all each and every website has its own design, layout, keyword and more. You cannot just follow what people said and place all your ads in the webpage and then hope that your CTR will increase. Do your own experiments on placing ads in different positions and find out which ad is performing very good. Some more you must have good traffic to your website.