tag:blogger.com,1999:blog-3722233.post1405472885752241534..comments2020-02-19T03:43:18.369-05:00Comments on Computational Complexity: T/F - No Explanation needed VS T/F-Explanation needed.Lance Fortnowhttp://www.blogger.com/profile/06752030912874378610noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-3722233.post-64043875497386476762013-10-01T21:29:41.124-04:002013-10-01T21:29:41.124-04:00I had a sophomore math class MIT (18.25: groups, r...I had a sophomore math class MIT (18.25: groups, rings, fields) where our grade was based on 3 open-ended, open book exams consisting of 10 True / False questions. Scoring for each exam was +10 for the right answer, -10 for the wrong answer, 0 for no answer, but +200 for the exam if you had 10 wrong answers. Needless to say, there were more than a few -80 scores.Barryhttps://www.blogger.com/profile/15601407170512828091noreply@blogger.comtag:blogger.com,1999:blog-3722233.post-21431353604124688582013-09-16T12:44:25.195-04:002013-09-16T12:44:25.195-04:00The question hinges around whether the respondent ...The question hinges around whether the respondent is expected to include the "if" as part of the question. That is, are they expected to say whether "|- X => Y" is true, or are they expected to choose between "X |- Y is true" "and X |- Y is false".<br /><br />All three of these statements are correct, so I don't think it's a fair question to eliminate "false" as a correct answer.<br /><br />If they have to explain their answer, then of course you might say they answered "false" for the wrong reason.<br />Lex Spoonhttps://www.blogger.com/profile/13859632965228608649noreply@blogger.comtag:blogger.com,1999:blog-3722233.post-78530885241887874332013-09-12T01:30:48.705-04:002013-09-12T01:30:48.705-04:00Off topic again: does anybody know when are the ST...Off topic again: does anybody know when are the STOC 2014 and CCC 2014 call for papers announced? (The level of unprofessionality is astounding.) Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-33651561837816340062013-09-11T21:22:11.728-04:002013-09-11T21:22:11.728-04:00What about a universally quantified statement that...What about a universally quantified statement that is false and if you try to prove it true you get to a point where "5 < 3" needs to be true. A student who gets there and puts a QED after that had a chance to see their answer was wrong but just mechanically did a proof without understanding what they were doing and moved on.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-78642745564891238762013-09-11T06:07:05.845-04:002013-09-11T06:07:05.845-04:00I second Anon 2: this is a very poor question.I second Anon 2: this is a very poor question.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-90988250862171426502013-09-10T11:54:38.462-04:002013-09-10T11:54:38.462-04:00For a introductory math subject, one quiz question...For a introductory math subject, one quiz question was a two-parter, where the first part required them to do some simple algebra to obtain a result, and the second part required them to use a different technique to verify the result. One student made a mistake in the first part, so got the wrong result. They then fudged the verification, essentially by skipping the penultimate step and going straight to the conclusion that the original result was correct.<br /><br />Of course, this "verification" didn't deserve any credit: either the student didn't know the technique, or missed the point of the question. Surprisingly, the student came up to me after receiving his graded quiz and attempted to argue that he should have got credit since the error in part b was a consequence of the error in part a. Talk about missing the point! He would have gotten credit if he'd pointed out that his part a answer was incorrect, but he didn't see satisfied with that!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-968978444435435102013-09-10T11:19:20.145-04:002013-09-10T11:19:20.145-04:00If I had been taking your exam, I would've wal...If I had been taking your exam, I would've walked up to you and asked, "Do you mean exactly 5 elements or at least 5 elements?" The wording is ambiguous, I think; a set can have 5 elements in it without those being the only 5.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-35367694934642896112013-09-10T09:34:50.564-04:002013-09-10T09:34:50.564-04:00Anon 1- I suspect someone has devised a set theory...Anon 1- I suspect someone has devised a set theory where a set really<br />can have a powerset of 5 elements. Fuzzy set theory? Some sort of Prob?<br /><br />Anon 2- I was trying to test BOTH things, which may be why so many got it wrong. Was it a terrible question? It did not correlate with other measures of who the good students are, so in that rigorous sense YES it was a terrible question. It might be good as a HW/discussion question. Since some said it<br />was OBVIOUSLY false it could also lead to a good discussion about the need<br />for rigorous thinking. GASARCHhttps://www.blogger.com/profile/06134382469361359081noreply@blogger.comtag:blogger.com,1999:blog-3722233.post-15559844684724977982013-09-10T07:00:02.519-04:002013-09-10T07:00:02.519-04:00I found this to be a terrible question (though I a...I found this to be a terrible question (though I admit that, on first reading, I got it wrong). What exactly were you trying to test? Their knowledge of power sets, or their ability to parse logical statements? If the former, I would have just asked "Is there a set whose power set has 5 elements?" If the latter, I would have asked "Is the following statement true or false: for all A, (P(A) has 5 elements) => A is infinite."Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3722233.post-44342248121388316452013-09-10T05:33:46.597-04:002013-09-10T05:33:46.597-04:00A clearly has ~2.32 elements and is thus finite.A clearly has ~2.32 elements and is thus finite.Anonymousnoreply@blogger.com