A subjective approach Most recreational bettors use some form of the first method above. They gamble mostly for entertainment, and are not inclined to do any serious research. They just want a reason to watch an NFL football game on television. Hey, nothing wrong with that, so long as no serious money is involved. It can be cheap entertainment.
More serious gamblers use either the second method or the third method.
When first starting out to seriously beat pro football lines, almost all beginners begin with stats. A psychologist might say that hard core statisticians have a need for the solid feel of their predictions. In a strange way, the use of a mathematical formula can relieve users of the responsibility of losing. Many statisticians don't trust judgments nor opinions. They refuse to consider things like revenge, injuries, emotional letdowns, or other non-mathematical evidence.