Specify your odds:

Using Odds and Probabilities

Odds can be converted to probabilities, and probabilities can be converted to odds. By entering different odds in the box above you can get a feel for how the two are related.

For example:

• Odds of 1 (1 to 1) corresponds to a probability of 0.5
• Odds of 4 (4 to 1) means that it is 4 times as likely to be true as to be false, which corresponds to a probability of 0.8 (Probability it is true = 0.8; probability it is false = 0.2; odds = 0.8 / 0.2 = 4)
• Odds of 0.25 (odds of 1 to 4 in favor, or 4 to 1 against) means that it is 4 times as likely to be false as to be true, which corresponds to a probability of 0.2 (Probability it is true = 0.2; probability it is false = 0.8; odds = 0.2 / 0.8 = 0.25)

Either odds or probabilities can be used to quantify the amount of confidence you have in a belief. Odds of 1 (probability = 0.5) means you are completely uncertain whether it is true or false. Odds of 10 to 1 in favor means you are pretty confident it is true. Odds of 10 to 1 against means you are pretty confident it is false.

Using odds has some advantages:

• Using odds helps keep you from setting your confidence at 0% or 100%
• Using odds makes it easy to update your beliefs in response to new evidence
• The idea of a "fair bet" can help you quantify your level of confidence