
Probability and Statistics Basic Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
April 2nd, 2012, 12:40 AM  #1 
Newbie Joined: Apr 2012 Posts: 7 Thanks: 0  Confusing probability question
A student is taking a multiplechoice 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! 
April 2nd, 2012, 05:39 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] 
April 2nd, 2012, 05:44 AM  #3  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,935 Thanks: 1129 Math Focus: Elementary mathematics and beyond  Re: Confusing probability question Quote:
 
April 2nd, 2012, 06:40 AM  #4  
Senior Member Joined: Dec 2011 Posts: 277 Thanks: 1  Re: Confusing probability question Quote:
Different people have different problemsolving 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) + P(CCCC)" />  

Tags 
confusing, probability, question 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
confusing probability questions  hoyy1kolko  Probability and Statistics  13  June 4th, 2011 04:22 PM 
Probability question (hard and confusing)  hoyy1kolko  Probability and Statistics  9  May 18th, 2011 08:49 AM 
Probability (confusing question)  hoyy1kolko  Probability and Statistics  5  April 15th, 2011 10:22 PM 
Probability question(confusing)  hoyy1kolko  Probability and Statistics  1  April 9th, 2011 08:54 AM 
Probability, help me, please, So confusing  daivinhtran  Probability and Statistics  1  March 29th, 2011 04:53 PM 