The old rule of Bayes - a derivative of a complex mathematical formula, but in order to use Bayes' rule in everyday life, not necessarily understand the math.
So Bayes' rule is one of the theorems in probability theory, to answer the question: "When you are faced with new information as it is to change your confidence?" We are talking about the decision-making under uncertainty, and how we need to revise our theories As new facts. It can also help us to make a decision in the cases where we have very few factors, as well as to avoid the common pitfalls and errors in our thinking. For this we need only apply the formula that has worked for hundreds of years.
Here is an example. For example, Ivan is 20% sure that the training helped him to stay energetic throughout the day. But the question arises, on what this confidence based? Here it is necessary to assume that the hypothesis is not true, and wonder - what would happen if the hypothesis were true?
Our Ivan must ask ourselves: how often I feel a surge of energy? If only one day out of three, he may consider the evidence of the theory of weak and, therefore, his faith was true. If he feels sluggish every day, the proof of the truth of the theory of Bayesian strong.