Logistic regression uses the concept of odds ratios to calculate the probability. This is defined as the ratio of the odds of an event happening to its not happening. For example, the probability of a sports team to win a certain match might be 0.75. The probability for that team to lose would be 1 – 0.75 = 0.25. The odds for that team winning would be 0.75/0.25 = 3. This can be said as the odds of the team winning are 3 to 1.