I'm almost done with my thesis, supposed to defend in about a month, and I have recently discovered a huge error in the methodology of my study. It is essentially something I cannot correct due to a lack of data (data I couldn't measure due to money/facility restrictions.)

My adviser is terrific and we are going to discuss this at length tomorrow, but I was curious if anyone has encountered this type of situation and, if so, what did you do? I certainly can't defend a thesis that is, well... wrong. :-(

Thanks!