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Topic: Conditional Probability Question
Replies: 49   Last Post: Oct 18, 2001 2:34 PM

 Messages: [ Previous | Next ]
 mensanator Posts: 5,039 Registered: 12/6/04
Re: Conditional Probability Question
Posted: Sep 26, 2001 9:40 AM

>Subject: Re: Conditional Probability Question
>From: Virgil vmhjr2@home.com
>Date: 9/25/01 11:23 PM Central Daylight Time
>Message-id: <vmhjr2-DECB08.22331625092001@news1.denver1.co.home.com>
>
>In article <20010925234846.05795.00000711@mb-mf.aol.com>,
> mensanator@aol.com (Mensanator) wrote:
>

>> >Subject: Re: Conditional Probability Question
>> >From: Ray Vickson rvickson@engmail.uwaterloo.ca
>> >Date: 9/25/01 5:09 PM Central Daylight Time
>> >Message-id: <3BB10091.36487FAB@engmail.uwaterloo.ca>
>> >
>> >There is a difference between examining previous parts and not examining
>> >them. If you take out (i-1) parts and put them aside without examining
>> >them, the probability that the i'th part (which IS examined) will be
>> >defective is 1/100. Surprisingly, this is true even if i=100, so you are
>> >drawing from a box that contains only 1 part. However, everything
>> >changes if the set-aside parts are examined instead of ignored.

>>
>> Why does it change?

>
>One's evaluation of probability is generally dependent on one's
>state of knowledge at the time of the evaluation. Each part
>examined, up to finding the defective part, changes one's state of
>knowledge.

I don't see that. What changes is that on every inspection, the probabilty of
finding the part goes from 1/100 to 1/1. But that is _not_ the probability that
the part is _at_ position i. It is the probability of finding it at postion i
_combined_ with the probability that it is _not_ at posititions i-1. And if you
do the correct math, you'll see that this is 1/100 for every i.

And the probability the ith part is defective does not change based on your
knowledge of the previous i-1 inspections, so it doesn't matter whether you
inspect them or not.

Date Subject Author
9/25/01 Aaron Davies
9/25/01 Randy Poe
9/25/01 Aaron Davies
9/26/01 Kevin Foltinek
9/26/01 mensanator
9/27/01 Kevin Foltinek
9/27/01 Aaron Davies
9/27/01 mensanator
9/25/01 Steve Wright
9/25/01 Timothy E. Vaughan
9/26/01 Lionel Barnett
9/25/01 Virgil
9/25/01 Ray Vickson
9/25/01 mensanator
9/26/01 Virgil
9/26/01 mensanator
9/26/01 Virgil
9/27/01 mensanator
9/27/01 The Scarlet Manuka
9/27/01 mensanator
9/27/01 Virgil
9/27/01 Aaron Davies
9/28/01 mensanator
9/26/01 Ray Vickson
9/26/01 mensanator
9/27/01 Virgil
9/27/01 mensanator
9/27/01 mensanator
9/27/01 Virgil
9/28/01 mensanator
9/28/01 Virgil
9/28/01 David Lloyd-Jones
9/28/01 mensanator
9/29/01 David Lloyd-Jones
9/29/01 mensanator
9/29/01 David Lloyd-Jones
9/29/01 mensanator
9/29/01 David Lloyd-Jones
9/29/01 mensanator
9/29/01 Virgil
9/29/01 mensanator
9/29/01 Lynn Kurtz
9/27/01 Aaron Davies
9/27/01 mensanator
9/27/01 Virgil
10/17/01 Mike Mccarty Sr
10/18/01 Virgil
9/27/01 Randy Poe
9/25/01 mensanator