This link examines the audience/speech link. It also uses a speech topic of High Blood Pressure to indicate the ethical considerations (standards) to maintain.
1a. Ethics: Some people believe that body type and weight are maintained by their genetics. They do not believe that they should alter their diets. Many people eat cultural foods, according to their ethnicities. Therefore, if they change their eating habits, they feel unethical about betraying their cultures. Another ethical part of issue is religion. Some people's religions prohibit them from taking medicines to monitor blood pressure.
Here are websites about race and blood pressure/ethics: http://hyper.ahajournals.org/cgi/content/full/41/3/463
Code of ethics:
1 b. Standards: Audience members must maintain behavioral standards of proper eating, proper exercise, limiting alcohol, and refraining from smoking.
2a. Plan for Credibility includes: researching books and online sources about hypertension, conducting campus surveys and interviews of students' eating and exercise behaviors, interviewing and surveying doctors, nurses, and health care professionals (dieticians, etc.).
2b. Plan to access audience's feelings about topic: Interviews, surveys, and questionnaires will be used to access their ...
This posting discusses the value of speech audiences and is well-presented with details.