0
   

Binomial probability function vs simple theory

 
 
Reply Tue 19 Mar, 2013 09:39 am
What is the probability of rolling exactly two sixes in 6 rolls of a die?

Solution by Binomial Probability function is
(6C2)*((1/6)^2)*((5/6)^4) = (15*((5)^2))/(6^6)

But by basic probability understanding
Probability = successful outcome/ total possible out come
So that way the probability should be 15/ (6^6)

I know that second calculation is not giving the right answer, but some how not convinced on why it is wrong as I don’t see approach being wrong.


Can someone help me understand why second approach is wrong?
  • Topic Stats
  • Top Replies
  • Link to this Topic
Type: Question • Score: 0 • Views: 459 • Replies: 1
No top replies

 
jespah
 
  1  
Reply Tue 19 Mar, 2013 09:52 am
@ask-me-abhi,
Hmm, thinking about this logically, rather than mathematically -

roll #1 - one chance out of six to roll a six
roll #2 - one chance out of six to roll a six
etc.

Can also be put as -
roll #1 - five chances out of six to roll a non-six
roll #2 - same as above, etc.

We also care about there being 2 rolls of six, so the condition of one roll of six must be fulfilled, and then it has to be fulfilled a second time, but only a second time. E. g. if the first roll of six happens on roll #6, that's no good.

I don't know if this is helping, or if it's confusing (and I apologize if it's the latter). Haven't thought about straight logic problems in years; thanks for the opportunity to do so.
0 Replies
 
 

Related Topics

 
  1. Forums
  2. » Binomial probability function vs simple theory
Copyright © 2024 MadLab, LLC :: Terms of Service :: Privacy Policy :: Page generated in 0.06 seconds on 11/15/2024 at 07:36:41