Question

A team of medical students doing their internship have to assist during surgeries at a city hospital. The probabilities of surgeries rated as very complex, complex, routine, simple or very simple are respectively, 0.15, 0.20, 0.31, 0.26, .08. Find the probabilities that a particular surgery will be rated complex or very complex 

Answer 1

Let E₁, E₂, E₃, E₄ and E₅ be the events that the surgeries are rated as very complex, complex, routine, simple and very simple respectively.

∴ P(E₁) = 0.15

P(E₂) = 0.20

P(E₃) = 0.31

P(E₄) = 0.26

And P(E₅) = 0.08

P(complex or very complex) = P(E₁ or E₂)

⇒ P(E₁ ∪ E₂) = P(E₁) + P(E₂) – P(E₁ ∩ E₂)

= 0.15 + 0.20 – 0

= 0.35   .....[∵ All event are independent]