Compare and contrast the differences between Secondary and Primary research

(1)Distinguish between probability and nonprobability samples. Why are nonprobability samples so popular in marketing research? Is their popularity justified?

(2)It has been said that, to some degree, coding of open-ended questions is an art. Would you agree or disagree? Why?

(3)Please compare and contrast the differences between Secondary and Primary research?

Which is more valuable to the marketer? Defend your position.