If half the llth graders have failed, and Daniel is in the llth grade,
the:
A. he has definitely failed B. there is a 50% chance he failed C. 
there is a 75% chance he failed D.  He has definitely not failed.

Hi fido123-ga,

The answer to this question is B - there is a 50% chance he has
failed.

Think of all 11th graders as a set...if half of them have failed, then
that means there is a probability of 0.50 that a randomly chosen 11th
grader will have failed. This question assumes that Daniel is a
randomly selected 11th grader since no other information is available.

Cheers!

answerguru-ga

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Request for Answer Clarification by fido123-ga on 31 Dec 2002 18:06 PST

Does it not mean that if 50% failed and Daniel is still in the llth
grade, Daniel indeed failed.

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Clarification of Answer by answerguru-ga on 01 Jan 2003 00:42 PST

The way the question reads, it does not imply that the 11th graders
have failed the grade itself, but perhaps a test or quiz. In order to
deduce that the failure being discussed is being held back in the 11th
grade, it would have been made explicitly clear.

answerguru-ga