I'm sitting in a meeting for my kids' school... they did a parent survey. They only got 160 responses out of 350 families... To me that seems like a REALLY HEALTHY sample... and I'm no statistician - but I think 45% is pretty damn skippy good.... and might even be called "statistically significant" sample. The High School science teacher in the room flat out disagreed with me and told me I wasn't being mindful of the families that didn't respond and that I was trying to silence them. He then likened our survey to the US census and tried to make it sound like we're trying to oppress some families.... Maybe my basic statistical sense is off... but a 45% response rate is PRETTY DAMN GOOD... and science man can f$%& off back to the hippie hole he crawled out of.