I don’t believe the results from any study that doesn’t discuss their methodologies, or when they have flawed methodologies. For instance, I have trouble believing any study where guys report their own sizes on the internet.
Lifestyle condom manufacturers did a study (http://www.betterpenis.info/size.htm) where they actually had women measuring the guys themselves with a ruler. Now that’s a good testing methodology.
BUT, I started to even wonder about that study. I read from a different article that Lifestyle offered guys a free drink at this Cancun nightclub to participate in the study and they got over 300 participants. I though about it and wondered how many small guys would actually expose themselves to women holding a ruler for a beer? For a small guy that would probably be the most humiliating thing he could ever set himself up for.
So then you have to wonder if the volunteers were more likely to be the average sized to big sized guys at this nightclub? However, it’s still probably yielded the most accurate results to date.