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April 2nd, 2012, 01:40 AM | #1 |
Newbie Joined: Apr 2012 Posts: 7 Thanks: 0 | Confusing probability question
A student is taking a multiple-choice exam in which each question has 4 choices. Assuming that she has no knowledge of the correct answers to any of the questions, she has decided on a strategy in which she will place 4 balls (marked A,B,C,D) into a box. She randomly selects 1 ball for each question and replaces the ball in the box. The marking on the ball will determine her answer to the question. There are 4 multiple choice questions on the exam. (a) What is the probability that she will get 4 questions correct? (b) At least 3 questions correct? (c) No more than 2 questions correct? My teacher left early since he had to go somewhere, so he didn't explain to us how to do this question. Again, much help would be very appreciated! |
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April 2nd, 2012, 06:39 AM | #2 |
Newbie Joined: Apr 2012 Posts: 7 Thanks: 0 | Re: Confusing probability question
Attempted to work these out. But my brain is all clustered atm.. I really need to work on my probability/mathematics skills. (a) If it's a 1/4 chance of getting one right for each qq. 4 qq's = 16 possible chances, so 4/16 to get 4 qq's correct. (25%)? (b) Confused with the wording [at least 3 qq's correct] (c) Confused with the wording for this as well [no more than 2 qq's correct] |
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April 2nd, 2012, 06:44 AM | #3 | |
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,912 Thanks: 1110 Math Focus: Elementary mathematics and beyond | Re: Confusing probability question Quote:
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April 2nd, 2012, 07:40 AM | #4 | |
Senior Member Joined: Dec 2011 Posts: 277 Thanks: 1 | Re: Confusing probability question Quote:
Different people have different problem-solving style preferences. Well, I'll just follow [color=#00BF00]greg1313[/color]'s approach. P(At least 3 questions correct) =P(3 questions correct or 4 questions correct) =P(3 questions correct) or P(4 questions correct) =P(3 questions correct and 1 wrong) or P(4 questions correct) | |
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