
Advanced Statistics Advanced Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
May 13th, 2008, 06:07 PM  #1 
Newbie Joined: May 2008 Posts: 4 Thanks: 0  Tricky question for me
Hi, I need some help with the following question. The production of a certain machine has a 5% of producing a faulty machine, there is a 0.91 chance that the faulty machines will be discarded and a 0.03 chance that a working machine will be discarded. How many of the machines in the discarded pile are faulty? Answer in percent. I could really use some help with this one. Thanks. 
May 14th, 2008, 03:26 AM  #2 
Senior Member Joined: May 2007 Posts: 402 Thanks: 0 
Here's a way to do this without using any statistics or probability. Say you have 2000 machines. Now, 5% of them are faulty, or in other words 100 machines. This gives us 1900 machines to be working. Also, 91% of the faulty ones will be discarded  91 machines. As for the working ones, 3% will be discarded  57. So, we have the total number of discarded ones  57+91=148 and hence the percentage of the faulty machines in the discarded pile is 91/148 ≈ 61.48%.

May 15th, 2008, 06:24 AM  #3 
Newbie Joined: May 2008 Posts: 4 Thanks: 0 
Ahh I see, smart. Thanks! 

Tags 
question, tricky 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Tricky probability question  can anyone help?  nforrin  Advanced Statistics  12  July 16th, 2013 08:39 PM 
A even more tricky question  wuzhe  Algebra  0  November 30th, 2012 06:30 PM 
tricky bonus question help!  everettjsj2  Calculus  9  February 27th, 2010 05:33 PM 
tricky derivative question  suomik1988  Calculus  2  January 31st, 2010 08:25 PM 
Tricky test question  cknapp  Real Analysis  3  October 14th, 2009 01:08 PM 