The Student Room Group

Need some probability help

We have a large population of students. Ten percent are left handed, thirty percent at blue eyed and five percent are both. What is the probability that:

1) a student chosen at random is neither
2) a student chosen at random is left handed but not blue eyed
3) a student chosen at random is not left handed but blue eyed

I believe that the first part is 0.65. However I can't get the other two as the probabilities i calculate, together with the 0.05 in the question, sum to greater than one.
Reply 1
Avatar for TeeEm
TeeEm
19
Original post by pineapplechemist
We have a large population of students. Ten percent are left handed, thirty percent at blue eyed and five percent are both. What is the probability that:

1) a student chosen at random is neither
2) a student chosen at random is left handed but not blue eyed
3) a student chosen at random is not left handed but blue eyed

I believe that the first part is 0.65. However I can't get the other two as the probabilities i calculate, together with the 0.05 in the question, sum to greater than one.


draw a Venn diagram to see the regions
L = left-handed
B = blue-eyed
L ∩ B = both

1) You're finding 1 - L ∪ B
2) You're finding L \ B, which is L - L ∩ B
3) You're finding B \ L, which is B - L ∩ B
Original post by shawn_o1
L = left-handed
B = blue-eyed
L ∩ B = both

1) You're finding 1 - L ∪ B
2) You're finding L \ B, which is L - L ∩ B
3) You're finding B \ L, which is B - L ∩ B


So 0.65, 0.05, 0.25? Thanks for your help

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you