Screen Link: https://app.dataquest.io/m/432/the-naive-bayes-algorithm/3/using-bayes-theorem

P(New Message|Spam)=0.75

P(New Message|SpamC)=0.3334

&

P(Spam|New Message)

P(SpamC|New Message)

Ok so, I do understand that P(New Message|Spam) != P(Spam|New Message). It seems so simple but I’m just having a hard time describing the difference between those two.

What I understand is that P(Spam|New Message) is the probability that the new email is spam given that it’s a new email. But, what does P(New Message|Spam) means then? It’s the probability that it is a new message given that it’s spam?

Would really appreciate a little bit of clarification here.

Thank you very much.

Maximilien