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Anonymous Wed 16 Feb 06:21:38 2022 No.14234312 View Reply Original Report

Quoted By: >>14234325 >>14234339 >>14234613 >>14234675

Deck of cards probability.

If I pull a card at random and ask you to guess the card you have a 1/52 chance of getting it right.

I then remove 10 random cards from the deck and discard them without you seeing them. I then pick a card and ask you to guess it.

Are your odds still 1/52? Does the absence of unknown cards affect the probability at all?

Anonymous

Anonymous Wed 16 Feb 2022 06:36:14 No.14234325 Report

Quoted By: >>14234333

>>14234312
Odds are still 1/52, the removal does not matter at all. If you shuffled a deck and removed 51 cards and asked me to guess the one card left, it would still be 52

Anonymous

Anonymous Wed 16 Feb 2022 06:43:00 No.14234333 Report

Quoted By: >>14234419

>>14234325
I agree. However my professor claims the probability can’t be accessed… he posted this-

Given that Probability is: P(A) = (# of ways A can happen) / (Total number of outcomes)
In the card scenario: P = (1 certain card can be drawn) / (50 cards)
ergo P=1/50
When P = (1 certain card can be drawn) / (¬50)
ergo P=1/¬50 1/¬50 = O
ergo P=O

As far as I’m concerned he is only taking into account the probability of a card being chosen, not the probability of the guess being correct

Anonymous

Anonymous Wed 16 Feb 2022 06:45:15 No.14234339 Report

Quoted By: >>14234359

>>14234312
There is a 0% chance of getting any of the removed cards and a 1/42 chance of picking one of the cards that was not removed.

Anonymous

Anonymous Wed 16 Feb 2022 07:02:13 No.14234359 Report

Quoted By:

>>14234339
That’s not what I’m asking. The question is “what are the chances of correctly guessing the card”

Anonymous

Anonymous Wed 16 Feb 2022 07:36:01 No.14234419 Report

Quoted By: >>14234600 >>14235591

>>14234333
You could determine some probability that the card was already discarded and then correct selection on what remains. Should come out to the same 1/52 though.
If one card has been discarded:
1/52 chance you pick a card that has been discarded. 0% chance the next card drawn matches.
51/52 chance you don't
and if you don't pick a discarded card there is a 1/51 chance the next card drawn is correct
51/52•1/51 + 1/52 • 0= 1/52

Anonymous

Anonymous Wed 16 Feb 2022 09:27:24 No.14234600 Report

Quoted By:

>>14234419
Yeah it’s still 1/52 because each card has the same probability of being discarded

Anonymous

Anonymous Wed 16 Feb 2022 09:34:43 No.14234613 Report

Quoted By: >>14234678

>>14234312
Break it down simpler: use 4 cards, A, B, C, and D.

If I remove 2 cards, and don’t tell you which ones I removed, the odds are still the same (1:4), because you still have to pick based on the original information of the 4 available cards.

Anonymous

Anonymous Wed 16 Feb 2022 10:32:29 No.14234675 Report

Quoted By: >>14234678 >>14235362 >>14235591

>>14234312
>Are your odds still 1/52?
no
>Does the absence of unknown cards affect the probability at all?
obviously
if the card you've guessed is still in the deck, then there's now a 1/42 chance of being correct
if the card you've guessed is not still in the deck, then there's no chance of being correct
the fact that you don't know which of these is the case doesn't change that fact

Anonymous

Anonymous Wed 16 Feb 2022 10:34:38 No.14234678 Report

Quoted By: >>14235003 >>14235384 >>14235591

>>14234613
wrong
if you do that, then the chance of being correct depends on which cards were removed
if the guessed card wasn't removed, there's now a 1/2 chance of being correct
if the guessed card was removed, there's now no chance of being correct
you don't know which of these is the case, but either of them is
see: >>14234675

Anonymous

Anonymous Wed 16 Feb 2022 13:58:04 No.14235003 Report

Quoted By:

>>14234678
>You can’t be this dumb, right??

Anonymous

Anonymous Wed 16 Feb 2022 16:21:14 No.14235362 Report

Quoted By:

>>14234675
Dude no. Think about what you just wrote. By that logic there’s a 1/2 chance of a correct guess if I remove 50 cards…

Anonymous

Anonymous Wed 16 Feb 2022 16:29:28 No.14235384 Report

Quoted By:

>>14234678
Yup

Anonymous

Anonymous Wed 16 Feb 2022 16:42:09 No.14235439 Report

Quoted By: >>14235498

This board is so bad. I can't believe people are actually arguing about this

Anonymous

Anonymous Wed 16 Feb 2022 17:01:39 No.14235498 Report

Quoted By: >>14235514

>>14235439
Do you agree it’s 1/52 though?

Anonymous

Anonymous Wed 16 Feb 2022 17:05:08 No.14235514 Report

Quoted By: >>14235550

>>14235498
Yes of course

Anonymous

Anonymous Wed 16 Feb 2022 17:16:32 No.14235550 Report

Quoted By: >>14235600

>>14235514
That’s good to hear. My professor has convinced half the class missing cards affects the probability. I feel like I’m going insane

Anonymous

Anonymous Wed 16 Feb 2022 17:30:58 No.14235591 Report

Quoted By:

>>14234675
>>14234678
I was gonna disprove you but >>14234419 already proved you wrong

Anonymous

Anonymous Wed 16 Feb 2022 17:34:02 No.14235600 Report

Quoted By:

>>14235550
Send him a private email (don't embarrass him publicly, people don't respond well to that)

Here's what you tell him:
The probability of selecting your card is
(probability that it was one of the 10 * the probability of selecting given it was one of the 10) + (probability that it was *not* one of the 10 * the probability of selecting given it was *not* one of the 10)

The probability that your card was not one of the 10 removed is
$\frac{51}{52}\frac{50}{51}\frac{49}{50}\dots\frac{42}{43}=\frac{42}{52}$

So the total probability is:
$\frac{10}{52}*0 + \frac{42}{52}*\frac{1}{42} = \frac{1}{52}$

This should convince even the most stubborn retard

Anonymous

Anonymous Thu 17 Feb 2022 02:40:05 No.14237465 Report

Quoted By:

just make a repeated simulation where you see what percent of the time the picked card is the ace of spades, and whether that's affected by 10 cards being discarded or not

Anonymous

Anonymous Thu 17 Feb 2022 05:09:53 No.14237845 Report

Quoted By:

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