1.9.2.1 Base Rate Fallacy

It's important to note that in real-life situations, we often assume that,

 (| ) = ( |), this is known as the Base Rate Fallacy. In our situation, it would mean, the probability of you having Hypoillness in reality, given that you are experiencing 90% of its symptoms, is equal to the probability of you having the symptoms, given that you actually have Hypoillness

This is an incorrect assumption as the two situations are completely different. The probability of someone actually having Hypoillness, given the person is experiencing 90% of its symptoms can be much less if the symptoms of Hypoillness are similar across other illnesses like Flu or Fever. Whereas, the probability of someone having the symptoms given that the person actually has

Hypoillness ought to be high since it's natural to have the symptoms when the person actually has the illness. This can also be seen in our example where the two probabilities vary drastically ( | ) = 0.1125% while ( | ) = 90%