The answer is that references are always needed, but one exception is that you don’t need to refer to information that can be supposed to be generally known. This could apply to circumstances that the world is round or that The Beatles is a well-known band. Here it may be appropriate to warn against generalisations of the type: “Children of today spend less time with their parents than they did a couple of generations ago.” If this statement is essential to your work, what you state needs to be corroborated or modified with reference to sources.
Another exception is that the references in your bibliography must be only those you have actually used and referred to in your text. Oral communication is not usually included in the list of works cited but it must be referred to in the running text or in a footnote. However, regarding interviews and polls, the guidelines for references may differ between academic disciplines. Always ask your tutor or teacher if you are unsure about how to cite and quote properly.