truman Posted November 30, 2012 Share Posted November 30, 2012 I take it you mean this question. I came up with the random answer of Jar. If I had chosen an answer from the list it wouldn't have been a random answer, because I would have used method and conscious thought to select it. My answer of jar is extremely likely to be the incorrect answer and because there are infinite possible random answers the possibility of getting it right is 1 - ∞ I'm having a hard time deciding what the question is... Link to comment Share on other sites More sharing options...
RichJay Posted November 30, 2012 Share Posted November 30, 2012 There was a post on the understanding uncertainty blog about this last year. Four possible answers are given based on different interpretations of the question. http://understandinguncertainty.org/probability-paradox My favourite bit is at the end... Maybe the main lesson is: ambiguity and paradox are often the basis for a good joke. Link to comment Share on other sites More sharing options...
maxmaximus Posted November 30, 2012 Share Posted November 30, 2012 I'm having a hard time deciding what the question is... Then you are giving it to much thought, the questioner is quite clear in what they want. If you choose an answer to this question at random, what is the chance you will be correct? They simply want you to choose a random answer; and then give the likelihood of being correct. The list of apparent answers is irrelevant and not part of the question. Link to comment Share on other sites More sharing options...
andygardener Posted November 30, 2012 Share Posted November 30, 2012 Err..3, no 4.8, 30%? I guess the answer is something to do with multiplying out the percentages. 4 answers, 2 of which are the same, so you are left with 3 answers of equal probability. You have to randomly pick so the randomisation process gives you a 25% chance of picking B 25% chance of picking C and a 50% chance of picking A/D So 25% of the time you pick B which has a 1/3 probability of being correct. 25% of the time you pick C which has a 1/3 probability of being correct. 50% of the time you pick A/D which has a 1/3 probability of being correct So the answer is..err something to do with the difference between the 25% and the 50% multiplied by 1/3..probably. I give up. Edit, actually thinking about it as the question relates to a single choice rather than multiple choices the answer is 1/3. ---------- Post added 30-11-2012 at 18:13 ---------- Hang on, that's wrong. 1 in 12 chance that I pick B and it's right 1 in 12 chance that I pick C and it's right 1 in 6 chance that I pick AD and it's right So overall chance is (1/12+1/12+1/6)/3 Which is 11.1111 recurring percent. Link to comment Share on other sites More sharing options...
dosxuk Posted November 30, 2012 Share Posted November 30, 2012 If the OP had written the question correctly, it's a pretty simple 50% chance of being right - of the four options, the probability of selecting the correct answer at random is 25% (1:4). The chances of selecting that correct answer are 2:4, or 50%. However, by completely mangling the question in the way he did, he made the question unanswerable. Link to comment Share on other sites More sharing options...
Cyclone Posted December 1, 2012 Share Posted December 1, 2012 If the OP had written the question correctly, it's a pretty simple 50% chance of being right - of the four options, the probability of selecting the correct answer at random is 25% (1:4). The chances of selecting that correct answer are 2:4, or 50%. However, by completely mangling the question in the way he did, he made the question unanswerable. If the probability of selecting any of the answers is 25%, and 2 of the answers say "25%" then the chance of selecting one of those answers is "50%". However if you select "50%" then there was only a 25% chance of getting it correct, meaning that the answer is wrong. There is a 0% chance of any of those answers being correct, it's a paradox. ---------- Post added 01-12-2012 at 09:54 ---------- Err..3, no 4.8, 30%? I guess the answer is something to do with multiplying out the percentages. 4 answers, 2 of which are the same, so you are left with 3 answers of equal probability. You have to randomly pick so the randomisation process gives you a 25% chance of picking B 25% chance of picking C and a 50% chance of picking A/D So 25% of the time you pick B which has a 1/3 probability of being correct. 25% of the time you pick C which has a 1/3 probability of being correct. 50% of the time you pick A/D which has a 1/3 probability of being correct So the answer is..err something to do with the difference between the 25% and the 50% multiplied by 1/3..probably. I give up. Edit, actually thinking about it as the question relates to a single choice rather than multiple choices the answer is 1/3. ---------- Post added 30-11-2012 at 18:13 ---------- Hang on, that's wrong. 1 in 12 chance that I pick B and it's right 1 in 12 chance that I pick C and it's right 1 in 6 chance that I pick AD and it's right So overall chance is (1/12+1/12+1/6)/3 Which is 11.1111 recurring percent. No it isn't. Whatever answer is picked is wrong. There is no chance of guessing it correctly, which makes it impossible to answer because 0% is not an option. ---------- Post added 01-12-2012 at 09:56 ---------- I take it you mean this question. I came up with the random answer of Jar. If I had chosen an answer from the list it wouldn't have been a random answer, because I would have used method and conscious thought to select it. My answer of jar is extremely likely to be the incorrect answer and because there are infinite possible random answers the possibility of getting it right is 1 - ∞ I think you mean 1/∞, 1 - ∞ is -∞ and that is not a probability. I don't think you've correctly understood how multiple choice questions work though, you have to pick from the answers supplied, even if you do so at random. Link to comment Share on other sites More sharing options...
maxmaximus Posted December 1, 2012 Share Posted December 1, 2012 I think you mean 1/∞, 1 - ∞ is -∞ and that is not a probability. I don't think you've correctly understood how multiple choice questions work though, you have to pick from the answers supplied, even if you do so at random. 1 - ∞ or 1/∞ mean there is one chance in infinite chances of getting it correct, where does it say it’s a multiple choice question? And by picking one of the answers from the list you didn’t follow the instruction which asked you to choose a random answer. How can it be random if you are choosing it from a list? The question would have been worded choose an answer from the list below if they wanted you to choose one from the list, but they asked you to choose a random answer and then followed it with a list that as nothing to do with the question just to see if you would follow the instruction or assume the answer was in the list. By assuming the answer is in the list and trying to choose one of those answer you failed the test because you didn’t follow the instruction as set out in the question. Link to comment Share on other sites More sharing options...
dosxuk Posted December 1, 2012 Share Posted December 1, 2012 If the probability of selecting any of the answers is 25%, and 2 of the answers say "25%" then the chance of selecting one of those answers is "50%". However if you select "50%" then there was only a 25% chance of getting it correct, meaning that the answer is wrong. There is a 0% chance of any of those answers being correct, it's a paradox. When worded correctly, the question is actually two questions. The answer to the first gives you the answer to the second. ---------- Post added 01-12-2012 at 13:20 ---------- 1 - ∞ or 1/∞ mean there is one chance in infinite chances of getting it correct When writing probabilities, you use a colon. e.g. 1:∞ Link to comment Share on other sites More sharing options...
maxmaximus Posted December 1, 2012 Share Posted December 1, 2012 When writing probabilities, you use a colon. e.g. 1:∞ I'm probably thinking of betting odds. Link to comment Share on other sites More sharing options...
Cyclone Posted December 2, 2012 Share Posted December 2, 2012 1 - ∞ or 1/∞ mean there is one chance in infinite chances of getting it correct, where does it say it’s a multiple choice question? It has 4 answers listed. That's normally a good clue that it's multiple choice. And by picking one of the answers from the list you didn’t follow the instruction which asked you to choose a random answer. How can it be random if you are choosing it from a list? It can be a random choice from a defined set. The question would have been worded choose an answer from the list below if they wanted you to choose one from the list, but they asked you to choose a random answer and then followed it with a list that as nothing to do with the question just to see if you would follow the instruction or assume the answer was in the list. If you say so. By assuming the answer is in the list and trying to choose one of those answer you failed the test because you didn’t follow the instruction as set out in the question. I think you've jumped to entirely the wrong conclusion in an effort to be clever. ---------- Post added 02-12-2012 at 09:50 ---------- I'm probably thinking of betting odds. Either way 1:∞ or 1/∞ is normally written as 0. Link to comment Share on other sites More sharing options...
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