No, because I took a sexual psychology course in college, where I learned that there is very little variation in erect penis size from guy to guy. It can vary considerably when flaccid, which is what accounts for the "black guys are frikin' huuuuuge" myth.
There is also something called the "pelvic fatty pad", which is the layer of fat just below your stomach and just above your dong. If you have a lot of fat in that particular area, it can make your equipment look smaller and (probably) affect measurements.