Bayesian Probability Calculator

Check out this Bayes Probability Calculator made with python!

Bayes Theorem (1763) determines probabilities based on new information. This web app runs on a Raspberry Pi running Python.

Make more confident decisions.

If your medical test came back positive, what is the probability that you actually have that illness?

Have a scientific basis for your social anxiety.

If she smiled at me, what is the probability that she likes me?

Try to use short statements, like “student is using drugs” and “failed drug test”, or “Titanic will hit iceberg” and “received iceberg warning”. The new information should be indicative, but cannot be causal. For example, failing the drug test does not cause the student to use drugs. Bayes Theorem cannot be used for causal relationships like, “Do people like me?” with new information “I am wearing pink today”, because the new information may cause people to like you. Instead, the new information should be indicative, like “I was voted class President”.

Example,

On September 26, 1983, just three weeks after the Soviet military had shot down Korean Air Lines Flight 007, Stanislav Yevgrafovich Petrov was the duty officer at the command center for the Soviet nuclear early-warning system when it reported that a missile had been launched from the United States, followed by up to five more. Petrov judged the reports to be a false alarm. For this decision, he is credited as "the man who single-handedly saved the world".

https://en.wikipedia.org/wiki/Stanislav_Petrov

What possibility are you contemplating? [US nuclear first strike]

Enter the new information: [missile launch detected]

1. What is the probability(%) of [Us Nuclear First Strike] before you got this new information?

2. [Estimate: 5%, low, as relations are tense but the US is not suicidal]

3. What are the chances(%) of [Missile Launch Detected] if [Us Nuclear First Strike]?

4. [Estimate: 95%, the warning system is good]

5. What is the chance(%) that [Missile Launch Detected] happens even if [Us Nuclear First Strike] is false or didn't happen?

6. [Estimate: 8%, sometimes there are false positives, but rarely]

Based on [Missile Launch Detected], there is a 38.5% probability of [Us Nuclear First Strike].

That is roughly 8 to 5 odds against [Us Nuclear First Strike].

So, what would be your decision? Will you save the world?