Posted by Gina on Tuesday, October 2, 2012 at 5:25pm.
An urn contains 5 red balls and 10 white balls. 6 balls are randomly drawn and not replaced. What is the probability that 3 or fewer balls drawn are red?

Statistics  math  Reiny, Tuesday, October 2, 2012 at 5:40pm
could be 3 red, 3 white
could be 2 red, 4 white
could be 1 red, 5 white
could be all white
prob of those taken in order from top to bottom
= C(6,3) (5/15)(4/14)(3/13)(10/12)(9/11)(8/10)
+ C(6,2) (5/15)(4/14)(10/13)(9/12)(8/11)(7/10)
+ C(6,1) (5/15)(10/14)(9/13)(8/12)(7/11)(6/10)
+ C(6,0) (10/15)(9/14)(8/13)(7/12)(6/11)(5/10)
= .... you do the button pushing
Can you see the pattern ?

Statistics  math  Gina, Tuesday, October 2, 2012 at 6:25pm
The answer is supposed to be 0.04 + 0.25 + 0.42 + 0.24 = 0.95
However, when I do the math above, I get 0.01 + 0.03 + 0.04 + 0.04 = 0.12.
Where am I making the error in calculating this?
Answer This Question
Related Questions
 statistics  An urn contains white and red balls. Four balls are randomly drawn ...
 statistics  An urn contains white and red balls. Four balls are randomly drawn ...
 Pre Algebra Probability  Each of two urns contains green balls and red balls. ...
 MATH(STATISTICS)  Urn A contains R red balls and W white balls, urn B contains ...
 statistics  An urn contains 10 balls of which 6 are white, 3 are red and 1 is ...
 statistics  An urn contains 10 balls of which 6 are white, 3 are red and 1 is ...
 Math help?  I am kind of stuck on this one Each of two urns contains green ...
 Finite MathProbability  Suppose we have an urn with 10 white balls and 6 red ...
 Another math related question  Two urns both contain green balls and red balls...
 math  A box contains 6 red balls, 4 white balls, and 5 green balls. If three ...
More Related Questions