Originally posted by Keltamaksa Here's a little snack-sized puzzle. I saw this on a science magazine some years ago and modified it a little.
You're in a lab of a mad scientist. You see two identical containers on the table but you can't see their contents. When you look at the scientist, you notice that he's holding a fresh human brain in his hands. "One of those containers", he say ainer he had picked. "With what probability does that jar have another brain in it?"
Ok, assuming the scientist is telling the truth, also that the chance of having a liver in the jar at the start is 50%, tghere is only 1 item in the jars at the start, and that he "picks" a jar carefully that contains a brain in his second step:
After putting the brain you have seen into a jar the followjng startes are possible, each with an equal probability.
BB, E
B, B
LB, E
L, B
Now he carefully picks a jar with a brain in it and takes it out.
in only 1/4 of the cases will the jar have another brain in.
The probability would be different if the scientist had randomly picked an item out and got a brain.
Originally posted by PBE6 I think you have to assume the game is fair (i.e. the scientist picks randomly), otherwise you have to make several additional assumptions which are tenuous at best. Even if he doesn't, but you don't know about his scheme, you can still answer the question truthfully and correctly.
However, I think my original solution was wrong. This is a case of conditio ...[text shortened]... nce of the brain being from the 2 brain jar. My brain must have been in a jar at the time. 🙄
Originally posted by uzless Impossible to answer correctly since sex is determined by genetics. Both the man and the woman can have weak or strong biases toward male or female children that would skew the probability.
50% is the answer to this flawed question however.
No, 50% is the answer to the other 'flawed' question. 😛
But these alleged biases cancel each other out when considering large samples/populations.
Originally posted by AThousandYoung Where do you think the error in my solution is?
It looks like you've correctly identified the 8 ways the jars can be seeded, but you forgot about the ways the organ can be selected. There are 10 possibilities for the selection, not 8 (don't forget the two cases where the scientist could pick an empty jar).
Originally posted by ThudanBlunder Originally posted by PBE6 [b]I have yet to see you make one attempt at solving any of the problems in this thread. When are you going to start?
Originally posted by PBE6 http://www.timeforchess.com/board/showthread.php?threadid=50368 ??
What's your point?
My point is that I found that puzzle interesting. Duh.
Anyway, I would not attempt such a poorly worded puzzle as this no-brainer.
And I prefer to leave Bayes Theorem puzzles to those who still find them new and interesting.
Originally posted by ThudanBlunder My point is that I found that puzzle interesting. Duh.
Anyway, I would not attempt such a poorly worded puzzle as this no-brainer.
And I prefer to leave Bayes Theorem puzzles to those who still find them new and interesting.
I prefer to leave the heavy editing to those who can't write.
Originally posted by PBE6 I prefer to leave the heavy editing to those who can't write.
That's it, move the goalposts.
Writers edit all the time. And I may be dyslexic for all you know. So cut the crap.
The fact is you got the silver/gold coins puzzle wrong by making an unjustified assumption and you don't like being corrected, you being so smart an' all.
ThudanBlunder, you could learn a lot from most of the posts on this forum, but two people in particular spring to mind: AThousandYoung and XanthosNZ.
AThousandYoung is the only person who always seems to be willing to offer his solutions for scrutiny, even if he's not sure about their validity. He also raises questions about his and other's analyses. This has the effect of opening up the discussion, and usually leads to deeper understanding of the problem. His positive and inquisitive nature is a virtue you lack.
XanthosNZ, on the other hand, likes to close discussions. However, he does so by posting his (always correct) solution. He can be a jerk too, but he never fails to provide his solution along with his taunts, even if he feels the problem is "beneath him". His confidence and transparency in offering proof are two more virtues you lack, even if you do share his acerbic edge.
Both of these characters contribute much more to the forum than detractors like you. Pedantic criticism is only entertaining to or welcomed by the pedant. I for one think you are capable of much more, and would welcome your input on this problem as you obviously have mathematical expertise.
Originally posted by ThudanBlunder That's it, move the goalposts.
Writers edit all the time. And I may be dyslexic for all you know. So cut the crap.
The fact is you got the silver/gold coins puzzle wrong by making an unjustified assumption and you don't like being corrected, you being so smart an' all.
I am resisting the urge to flame you back, because it wouldn't get either of us anywhere.
I believe you said there was no a priori evidence for assigning equal probabilities to each of the outcomes in the coins puzzle. I believe there is no a priori evidence for assigning unequal probabilities to each of the events, either. I wouldn't call that a strong refutation of my solution. However, if you would provide me with the exact probabilities of each of the outcomes, I'll try to solve it again.
A mad scientist
25 Aug '06 22:391 edit
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