Probability Odds Question Two

Question

1.Chelsea is trying out for her school play.

Using subjective probability, she estimates

that she has an 80% chance of getting a part

and a 25% probability of landing a lead role.

a) What are the odds in favour of Chelsea

getting a part in the play?

Would this be right?

P(A) = 80%/100% = 4/5

P(A') = 1-4/5

=1/5

Odds in favour = A = P(A)/P(A')

= 4/5 / 1/5 = 4



b) What are the odds against her landing a

lead role?

Would this be right?

P(A) = 25%/100% = 1/4

P(A') = 1-1/4 = 3/4

Odds against = A = P(A')/P(A)

= 3/4 / 1/4 = 3

Answer 1

a) 80% b)75%

assuming the lead role is also a part in the play, then she has an 80% probability of getting a part in the play. It almost seems like a trick question as they give you 80% and then ask for it back, all the while tempting you to make some irrelevant calculations. leading role part is part of the 80%

b) she has a 25% chance at a leading role, subtract from 100% to get 100-25 = 75% of not getting a leading role

by the way, regardless what you do or calculate if you ever get a probability>1, you know you did something wrong. 100% is the maximum possible probability for anything. 3 could never be right, no matter what the problem.