Thread: Indepedant events.

I hope this isn't too long winded, I have most the answers, just need a check and some help on the last part.

Laser surgery to fix short-sightedness is becoming more popular. However, for some people, a second procedure is necessary. The following table lists the joint probability of needing a second procedure and whether the patient has a corrective lens with a factor (dioptre) of minus 8 or less.

This is supposed to be a table!

__________________ Vision corrective factor > -8, Vision corrective factor <= -8

1st procedure successful ___________0.66 ___________________0.15


2nd procedure required ____________0.05 ___________________0.14




a) Find the probability that a second procedure is required.

This is simply



b) Determine the probability that someone whose corrective lens factor is minus 8 or less does not require a second procedure.

This is


c) Are the events independent? Explain your answer.

I think the answer is yes, but I don't know how to explain

Originally Posted by Bushy

I hope this isn't too long winded, I have most the answers, just need a check and some help on the last part.

Laser surgery to fix short-sightedness is becoming more popular. However, for some people, a second procedure is necessary. The following table lists the joint probability of needing a second procedure and whether the patient has a corrective lens with a factor (dioptre) of minus 8 or less.

This is supposed to be a table!

__________________ Vision corrective factor > -8, Vision corrective factor <= -8

1st procedure successful ___________0.66 ___________________0.15


2nd procedure required ____________0.05 ___________________0.14




a) Find the probability that a second procedure is required.

This is simply



b) Determine the probability that someone whose corrective lens factor is minus 8 or less does not require a second procedure.

This is


c) Are the events independent? Explain your answer.

I think the answer is yes, but I don't know how to explain

(b) Pr(2nd procedure NOT required | corrective lens factor < -8) = 0.15/(0.15 + 0.14).

(c) Does Pr(2nd procedure NOT required | corrective lens factor < -8) = Pr(2nd procedure NOT required) ....?