From Bespin to Yavin, the “Star Wars Hit Probability Equation” predicts the outcome of any battle:

n is the number of “bad guys,” x is the number of “good guys,” and J is the number of Jedi present (if any).

The equation reads, “The probability of a bad guy hitting his target is equal to the inverse of all bad guys present plus the cube of the number of good guys present (plus one) plus the number of Jedi present (plus one) to the 10th power.”

So the presence of a good guy reduces the bad guys’ accuracy, and having even one Jedi present is bad news for the Empire.