I've written before about the questionable validity of results obtained from focus groups (you know, those demographically aligned groups of strangers we put behind one-way mirrors to fiddle with and discuss our products or ideas). Then along comes the book "What she's not telling you" and confirms what we have always dreaded: our focus group research is worth Nada. Zero. Nil.
Because the participants (women, in this case) weren't telling the truth (but that could go for men too).
Recommended reading BEFORE you finalize and test that one winning 'big idea' on yet another focus group:
"What She’s Not Telling You: Why Women Hide the Whole Truth and What Marketers Can Do About It."