My Math Forum  

Go Back   My Math Forum > College Math Forum > Advanced Statistics

Advanced Statistics Advanced Probability and Statistics Math Forum


Reply
 
LinkBack Thread Tools Display Modes
March 22nd, 2012, 02:47 PM   #1
Newbie
 
Joined: Feb 2012

Posts: 10
Thanks: 0

Probability, marbles

Hi, can someone check this and tell me if I am doing this correctly? I would really appreciate it!

Six marbles are chosen without replacement from a box containing 10 red, 8 blue, and 3 yellow marbles. Let X be the number of blue marbles chosen.
a) Find the probability distribution of X.
b) Find the mean of the random variable X

ok so for part a i did:

P(0B) (6 choose 0) 1*(0.10)^0 (0.3)^6 = 0.000729
P(1B) (6 choose 1) 6* (0.10)^1 (0.3)^5 = .001458
P(2B) (6 choose 2) 15 *(0.10)^2 (0.3)^4 = .001215
P(3B) (6 choose 3) 20 *(0.10)^3 (0.3)^3 = 0.00054
P(4B) (6 choose 4) 15 * (0.10)^4 (0.3)^2 = 0.000135
P(5B) (6 choose 5) 6 * (0.10)^5 (0.3)^1 = 0.00000180
P(6B) (6 choose 6) 1 * (0.10)^6 (0.3)^0 = 0.00000010

Is this right? Or am I doing this completely wrong? Some of the numbers I calculated aren't coming out right.
Ataloss is offline  
 
March 23rd, 2012, 11:43 AM   #2
Newbie
 
Joined: Feb 2012

Posts: 10
Thanks: 0

Re: Probability, marbles

I tried it again and I still am getting wrong answers
Ataloss is offline  
March 23rd, 2012, 08:42 PM   #3
Senior Member
 
Joined: Dec 2011

Posts: 277
Thanks: 1

Re: Probability, marbles

Quote:
Originally Posted by Ataloss
Six marbles are chosen without replacement from a box containing 10 red, 8 blue, and 3 yellow marbles. Let X be the number of blue marbles chosen.
a) Find the probability distribution of X.
b) Find the mean of the random variable X
Are you absolutely sure that the marbles are chosen without replacement?
If that's the case, I see that the event of drawing blue marbles are dependent, and the probability of success (i.e. to get blue marbles) is not the same for each draw. In other words, it can't constitute any probability distribution, don't you think???
Isbell is offline  
March 24th, 2012, 01:55 PM   #4
Math Team
 
Joined: Dec 2006
From: Lexington, MA

Posts: 3,267
Thanks: 407

Re: Probability, marbles

Hello, Ataloss!

Quote:
Six marbles are chosen without replacement from a box containing 10 red, 8 blue, and 3 yellow marbles.
Let X be the number of blue marbles chosen.

a) Find the probability distribution of X.

There are 8 Blue marbles and 13 Others.



soroban is offline  
Reply

  My Math Forum > College Math Forum > Advanced Statistics

Tags
marbles, probability



Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Probability Question With Four Containers Of Marbles EvanJ Advanced Statistics 1 March 19th, 2014 07:55 AM
Marbles shunya Algebra 8 March 6th, 2014 06:35 PM
Am I losing my marbles? mathkid Calculus 2 November 18th, 2012 09:54 PM
Joint probability density function, probability token22 Advanced Statistics 2 April 26th, 2012 04:28 PM
Marbles Soha Algebra 3 January 2nd, 2007 03:16 PM





Copyright © 2017 My Math Forum. All rights reserved.