s230.t1.F09

# s230.t1.F09 - required – expressions are sufficient...

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Statistics 230, Fall 2009 Midterm Test Time: 70 minutes (10 marks) 1. Letters addressed to individuals A,B and C are randomly placed in the three addressed envelopes, one letter per envelope. (a) List a 6-point sample space. (Be sure to make it clear what your points represent.) (a b c) , (a c b) , (b a c) , (b c a) , (c a b), (c b a) (b) List the sample points corresponding to each event and give the probability for the event. D: A’s letter goes in the correct envelope. 1/3 E: No letter goes in the correct envelope.1/3 F: Exactly one letter goes in the correct envelope.1/2

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(10 marks) 2. Five people get on an elevator at the ground floor and can get off at floors, 2, 3, …, 8. (a) What is the probability (i) they all get off at different floors. (ii) they all get off at the same floor (iii) two get off at one floor and three get off at another floor. (Calculations not

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Unformatted text preview: required – expressions are sufficient for (a)). (b) What assumption(s) underlies your solution to (a)? Comment briefly on how likely it is that your assumption(s) is valid. (10 marks) 3. In a slalom ski race 20% of competitors fail to finish (due to crashing or going off course), independently of other competitors. Calculate the probability (a) in a race with 8 competitors, exactly 2 fail to finish. (b) The 8 th competitor in a race is the second one who fails to finish (c) The 8 th competitor in a race is the second one who fails to finish, given that 2 of these 8 competitors fail to finish. Statistics 230, Fall 2009 Midterm Test Name: _______________________ Time: 70 minutes ID #: _______________________ Instructor/Section: M. LaCroix (1, 2, 5) __; C. Springer (3) __ ; S. Khan (4) __ PLEASE IND ICATE YOUR INSTRUCTOR/SECTION ABOVE....
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s230.t1.F09 - required – expressions are sufficient...

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