Final answer:
Speakers do not need to cite common knowledge, which includes obvious or general information widely known to the audience. Specific and less known data must be cited to ensure credibility.
Step-by-step explanation:
Speakers do not have to cite information that is common knowledge. Common knowledge refers to information that is widely known and accepted by most people within a certain audience. Examples include widely acknowledged facts like the name of the current president of the United States. However, specific data such as approval ratings, which the general audience may not know, would require citation. When giving a speech or presenting information, it's essential to practice ethical attribution by citing non-common knowledge sources, ensuring credibility and avoiding plagiarism.