Not to say what CW did was right, but I think this needs to be said as a public service announcement for others who might read this:
If you are offered a discount at a store (or anywhere) for answering a few questions, as soon as they ask you a personal question - such as your income, your employer, your address, your social, your birthdate, etc. - STOP. Do not give them that information. At that moment, tell them you are not going to provide that information for a discount. If the clerk pushes you, ask to speak with a manager right there and then. DO NOT ANSWER THE QUESTIONS.
A general survey will not ask you specific questions like that. They will ask for an age range (24-30; 31-49; etc.), a zip code only, etc. Anything more specific and it is not a simple survey.