The Magic Formula is a structure used for a brief talk to persuade. After much study, it appears to be more effective than more traditional structures when time is limited. It is described in Dale Carnegie's The Quick and Easy Way to Effective Speaking, and is covered in Dale Carnegie Training. In the course, the structure pans out like this:
(2 minute format):
1:40 An incident that happened to you
:20 The action you want the audience to take and the benefit they will receive for taking it.
In practice, it works for brief speeches of any length, such that you finish off with a twenty-second action-benefit phase.
Why is this so effective when, in general, testimony is not considered a trustworthy source for information? The Scottish theologian George Campbell, in a rebuttal to David Hume's On Miracles titled Dissertation on Miracles outlined one theory indirectly. Hume had doubted the testimonial basis for religious (read Christian) belief. Campbell argued that people tend to believe the claims of others, and that as children, that is our state and therefore it is the way God made us. In this argument, Campbell highlights the tendency of people to want to believe.
For those who doubt my ability to bring forth this information - I studied Scottish Enlightenment philosophers in college in an elective course. | 
