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# Fundamentals: Bayes' Theorem

In this Wireless Philosophy video, Ian Olasov (CUNY) introduces Bayes' Theorem of conditional probability, and the related Base Rate Fallacy.

Speaker: Ian Olasov, City University of New York.

## Want to join the conversation?

• How can make this practical?:
Do i need the exact probabilities of an hyphotesis and evidence to make it work?
Do i really have to calculte with the formula or we have to "internalize" this knowledge without calculating?
• Can somebody give the math proof of Bayes' Theorem?
• Given i have lets say P(A | B) = 0.5 then what will be P(A | (Inverse) B) = ?
• There's no rule for determining this, we don't know.

For example, the probability that I get a heads on a coin flip given that it's a Tuesday is 0.5, and it's also 0.5 given it's not a Tuesday. We'd say that the day of the week is independent of the result.

But the probability of me passing an exam given sufficient sleep might be 0.9, while my probability of passing given insufficient sleep might be 0.6. In this case, the result is not independent.
• What is the difference between conditional probability and regular probability?
• In a Conditional probability you are "measuring" the probability subject to a conditional variable (In the first example, the conditional variable is "sex", If the flu patient is a GIRL, then the probability is 0.20, if the flu patient is a BOY, then is 0)
• Between -: Ian says that "you have ALL of the symptoms you would have if you had hypothesitis"... So why are we assigning P(E|H) as 0.95 and why not 1, given that ALL symptoms are already there...!!

Thank you..
Regards
• You don't necessarily get all of the symptoms of a disease. In the case of hypothesitis, 95% of patients have all of its symptoms, but some may lack a headache or a sore throat for one reason or another.
(1 vote)
• What is the Software you have use to create this kind of animation
• Help me, please! I need to solve one question. Based on the current rating of a candidate and the results from the previous presidential elections, how to calculate the probability of a candidate winning the presidential elections in the first round? Thank you in advance
(1 vote)
• Re Bayes' Theorem
Why can't I just use P(H/E)= P(H and E) / P(E)
(1 vote)
• You can, but you never know P(H and E) is you don't know P(H) and P(E|H), or P(E) and P(H|E) (which's exactly what we're trying to find).
(1 vote)
• what does this have to do with philosophy ( I havent watched the video yet so i may answer myself )
(1 vote)
• Theology is a respected branch of Metaphysics using Abstract Thinking where Bayesian probability arguments are typically the most respectable. "this this and this are true, therefore, there is a high LIKELIHOOD that X is true, and X has a decent likelihood of being caused by a creator god, therefore I'm confident enough in that probability to think a god exists." While this sounds like gibberish to us, this is how many many arguments for the existence of god sound.