In: Statistics and Probability
You are trying to design a system that will determine whether someone has a PhD in music. You have the following information:
You stop someone on the street and play them a 5-second segment of Claire de Lune. They correctly identify the composer as Debussy. Based on the information above, what is the probability that this person has a music PhD?
P(correctly identify a composer | music PhD) = 0.85
P(correctly identify a composer | anyone else) = 0.02
P(music PhD) = 0.003
P(correctly identify a composer) = P(correctly identify a composer | music PhD) * P(music PhD) + P(correctly identify a composer | anyone else) * P(anyone else)
= 0.85 * 0.003 + 0.02 * (1 - 0.003)
= 0.02249
P(music PhD | correctly identify a composer) = P(correctly identify a composer | music PhD) * P(music PhD) / P(correctly identify a composer)
= 0.85 * 0.003 / 0.02249
= 0.1134