Illusionz Posted June 22, 2005 Share Posted June 22, 2005 I'm struggling with probability problems :hmm:...can anyone recommend a good book/site for probability? It'd be deeply appreciated Comparison Problem The probability that events E and F will both occur is 0.42 a. The probability that event E will occur.............................b.0.58 ----------------------- 30. In a group of 80 students, 24 are enrolled in geometry, 40 in biology, and 20 in both. If a student were randomly selected from the 80 students, what is the probability that the student selected would not be enrolled in either course? (A) 0.20 (B) 0.25 © 0.45 (D) 0.55 (E) 0.60 Quote Link to comment Share on other sites More sharing options...
Chelsea Posted June 22, 2005 Share Posted June 22, 2005 2. ans C using set theory 1-P(a union B) 1 - [p(A) + P(B) - P(A int B)] 80/80 - [24 + 40 - 20] / 80 (80 - 44) / 80 36 / 80 9/20 4.5/10 0.45 Quote Link to comment Share on other sites More sharing options...
ecodude Posted June 22, 2005 Share Posted June 22, 2005 2. the answer i am getting is ( C ). 0.45 . prob( choosing a student doing neither course ) = 36 / 80 . i m uploading an image file , a venn diagram . 1. at most one can say is that p( E) + p( F) = 1.42 . bcoz , p( E or F ) = p( E) + p( F) - p( E and F ) = 1 . => prob( E ) >= 0.42 . also prob( F ) >= 0.42 . so , in my view , a and b cannot be compared ( lack of info ) . note even if we don't assume that E & F are exhaustive like above , what p( E and F ) = 0.42 at best gives us is that prob that E occurs is at least 0.42 , and nothing more info .untitled.bmp Quote Link to comment Share on other sites More sharing options...
Chelsea Posted June 22, 2005 Share Posted June 22, 2005 1. P(e int f) = 0.42 P(e union f) = P(e) + P(f) - P(e int f) 1 = P(e) + P(f) - 0.42 P(e) + P(f) = 1.42 P(e) = 1.42 - P(f) max pblity P(f) can have is 1 then max value of P(e) = 0.42 so P(e) is less than 0.52 so a someone pls check chelsea Quote Link to comment Share on other sites More sharing options...
ecodude Posted June 22, 2005 Share Posted June 22, 2005 chelesa if max what p(f) can have is 1 , then 0.42 is minimum what p(e) can have , not the max Quote Link to comment Share on other sites More sharing options...
arjmen Posted June 22, 2005 Share Posted June 22, 2005 Some fairly usefull stuff: http://www.www.urch.com/forums/showthread.php?t=24356 1 Quote Link to comment Share on other sites More sharing options...
Illusionz Posted June 23, 2005 Author Share Posted June 23, 2005 Thanks a lot Chelsea,ecodude and arjmen :). Quote Link to comment Share on other sites More sharing options...
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