User blog comment:Nblonkenfeld/Wikia Media Survey/@comment-24155515-20140919212704/@comment-452-20140920224212

That depends of the goal of the research.

If the goal of the research is to show Wikia's advertisers that Wikia's audience spends money, then it is in Wikia's best interest for everyone who takes the survey to say they spend money, even if they do not.

Saying "I'm sorry, you said you spend $0, therefore you are not eligible to win an iPad mini" all but ensures that those people will go retry and say they spend money.

Edit:

To put it another way: Wikia knows what the advertisers want to hear, so they only give the chance to win an iPad mini to people who give the answers they want.