What is the difference between a purpose statement and a central idea? a purpose statement focuses on audience behavior, while a central idea focuses on the content of the speech. a central idea guides your decisions and choices as you prepare your speech, whereas a purpose statement becomes part of your final speech. a central idea focuses on the speaker's behavior, whereas a purpose statement focuses on the audience's behavior. a purpose statement focuses on the content of the speech, while a central idea focuses on audience behavior.