
Advanced Statistics Advanced Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
June 6th, 2017, 05:11 PM  #1 
Member Joined: Apr 2017 From: PA Posts: 45 Thanks: 0  A die is loaded so that the probability of a face coming up is proportional to the nu
A die is loaded so that the probability of a face coming up is proportional to the number on that face. The die is rolled with outcome X. Find V (X) and D(X). How would you find the Expected value E(x) and the variance V(x) for this problem? For this problem, I knew that the probability for each outcome would be x/21. And I knew that X=1,2,3,4,5,6 so I took the expected value of 1× (1/21)+2× (2/21)+3×(3/21)+4×(4/21)+5×(5/21)+6×(6/21) and got 3, then I tried to find the variance by using V(x)=E(x^2)(E(x))^2=12, but the answer was 3/4 for V(x). 
June 6th, 2017, 06:26 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,378 Thanks: 542 
Redo your arithmetic. Mean=91/21.

June 6th, 2017, 06:49 PM  #3 
Member Joined: Apr 2017 From: PA Posts: 45 Thanks: 0 
So is the procedure right?

June 6th, 2017, 10:19 PM  #4 
Senior Member Joined: Sep 2015 From: Southern California, USA Posts: 1,602 Thanks: 816  

Tags 
coming, die, face, loaded, probability, proportional 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Proportional counting  studio52  Elementary Math  1  May 12th, 2015 11:08 AM 
Loaded Dice Probability Question  Abstract3000  Probability and Statistics  1  February 25th, 2014 11:03 PM 
Proportional question please help  John90  Algebra  1  November 28th, 2012 11:12 PM 
A loaded test tube  Chikis  Physics  13  October 25th, 2012 09:38 PM 
Proportional question please help  John90  Applied Math  1  December 31st, 1969 04:00 PM 