tag:blogger.com,1999:blog-8677649049588007585.post3440439817515200955..comments2014-11-13T12:12:56.473ZComments on PL/SQL Challenge: Tricky choice tricks the quiz author! (4720)Steven Feuersteinhttp://www.blogger.com/profile/16619706770920320550noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-8677649049588007585.post-17794227095478045512011-07-19T13:59:57.340+01:002011-07-19T13:59:57.340+01:00Thanks, all! I will certainly follow the overwhelm...Thanks, all! I will certainly follow the overwhelming recommendation to not change the scoring. I will, however, strive to avoid such conditional statements in the choices, in the future, and stick instead to unconditional claims.Steven Feuersteinhttp://www.blogger.com/profile/16619706770920320550noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-32621436909335258592011-07-19T13:36:31.431+01:002011-07-19T13:36:31.431+01:00I'm with those who say to leave the choice as ...I'm with those who say to leave the choice as correct. The statement is true as written, since it said "if", not "if and only if".<br /><br />If the choice is false, then there must exist some answer which includes a 1, but in which the other numbers are not 2, 4, and 7. This cannot be true, since we know that the solution <b>must</b> include 2, 4, and 7, <i>regardless</i> of the value of the fourth number. Just because the second part of the condition is true regardless of the truth of the first part does not make the statement false.<br /><br />Of course, if there had been enough evidence to rule out the possibility of 1 being in the solution at all, then scoring would be trickier. I'd still hold that the statement is true, personally, but one could argue against it.Davidhttp://www.blogger.com/profile/01674531537929187560noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-10552290559447326492011-07-19T08:59:20.953+01:002011-07-19T08:59:20.953+01:00Hello All,
This thread seems to become more and m...Hello All,<br /><br />This thread seems to become more and more "colorful" :) :)<br /><br />However,<br /><br />1. As Wim said above, F => T is true, and, in our case we have in fact T => T, which is also true.<br /><br />2. Roger probably felt the same as me about the IF statement, however, as JHall62 correctly underlined above, the IF statement would have been incorrect only if it were written as<br /> "IF and ONLY IF "1" is in the solution, then ...", which would have meant that, <br /> if 1 is NOT in the solution, then the second part might be false, which is not the case.<br /><br /> Or, in your terms, if you would say "If and ONLY if the phone rings today, then milk is white",<br /> which is obviously false.<br /><br />To just make an analogy with a recent quiz from the SQL competition, if we have a WHERE condition like <br />"col_a > ALL (select col_b from mytable)",<br />then if the inner select returns no rows, the <br />WHERE condition itself always TRUE, <br />because there is no "sample case" that would contradict it.<br />On the other hand, a similar condition with<br />ANY instead of ALL is always false.<br /><br />Thanks & Best Regards,<br />Iudith MentzelAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-70686289710392715502011-07-19T07:14:02.418+01:002011-07-19T07:14:02.418+01:00The fact that if your phone rings today, milk is i...The fact that if your phone rings today, milk is indeed white, and worse, even it it doesn't ring, it is white, so thank you for proving our point, unintentionally. It is a True statement! Roger, this quiz is about logic. And in this game, statements like that are logic statements and could not be handled else. Language could be ambiguous, but not in this situation. <br /><br />What can be discussed is the usefulness of the specific statement, but not the truth value of it.Wim de Langehttp://www.blogger.com/profile/05505341375827859005noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-90782201853563484862011-07-18T20:20:31.932+01:002011-07-18T20:20:31.932+01:00I was the 2nd one who brought this to Steven's...I was the 2nd one who brought this to Steven's attention.<br /><br />You'd be all right, if we were talking about boolean expressions. But we don't, it's a real world sentence. And the question was about a "valid conclusion". In this case, the conclusion was wrong, that it depends on 1, so for me the answer was wrong itself (as in "If my phone rings today, milk is white").<br /><br />I nevertheless wouldn't rescore all the boolean guys... ;-)<br /><br />RogerAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-50701901742344739962011-07-18T19:09:22.289+01:002011-07-18T19:09:22.289+01:00If you take a look at a truth table for implies, t...If you take a look at a truth table for implies, then F => T is a true expression. So no rescoring needed.Wim de Langehttp://www.blogger.com/profile/05505341375827859005noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-46330330340733387442011-07-18T16:28:25.309+01:002011-07-18T16:28:25.309+01:00Why should the choice be re-scored? If 1 is in the...Why should the choice be re-scored? If 1 is in the solution then 2,4 and 7 are too. That is a true statement!<br /><br />Looking at the numbers in turn 3, one at a time, we rule out 3, 5 and 6. 1 is left as the only number that fits in all three turns. We derived that 2,4 and 7 must be in the solution. Isn't that pretty much what the choice says?<br /><br />Who says we must start out by making a rule from the obvious result of turn 3, telling us that 2,4,and 7 are in the solution no matter what? And what difference does it make?<br /><br />The explanation is consistent with the choice.<br /><br />MikeMikehttp://www.blogger.com/profile/04855911908563127732noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-26136312779235707432011-07-18T15:45:10.134+01:002011-07-18T15:45:10.134+01:00I must agree with Iudith and jhall62. The choice i...I must agree with Iudith and jhall62. The choice is correct. No rescoring needed from my point of view.<br /><br />Kind regards,<br />MargaAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-54757716995000979712011-07-18T14:40:10.369+01:002011-07-18T14:40:10.369+01:00The choice "If 1 is in the solution then the ...The choice "If 1 is in the solution then the other numbers must be (2, 4, 7)" is a correct choice. Had the predicate been phrased as "If, and only if, 1 is in the solution," then the choice would have been incorrect since the third turn requires that the numbers (2, 4, 7) be in the solution.<br /><br />Because the choice is correct, there is no reason to recalculate scores.<br /><br />Because the third turn is sufficient to determine three of the four digits (which greatly facilitates finding the solution), the quiz should not be classified as advanced.jhall62http://www.blogger.com/profile/10339038131928463003noreply@blogger.comtag:blogger.com,1999:blog-8677649049588007585.post-40457405129983693322011-07-18T14:31:29.741+01:002011-07-18T14:31:29.741+01:00Hello Steven,
As one of those who raised this pro...Hello Steven,<br /><br />As one of those who raised this problem, I still think the following:<br /><br />Judging SOLELY by the boolean logic rules, if two statements A and B are both TRUE,<br />than the implication "A implies B" is also TRUE.<br /><br />It (that is, the implication itself !) CANNOT be false by any means, because that would require at least one case where A is TRUE and B is FALSE.<br /><br />The only problem with this "IF" statement is that it is "weeker" than the assumptions allow it.<br /><br />It could have been replaced with 2 stronger statements, one saying that "1" is in the solution, and the other one saying that "2,4,7 are in the solution", both of them being true.<br /><br />The "IF" statement could have been stronger in case that we could only conclude from the clues that "ONLY" if 1 is in the solution, then 2,4,7 are also in the solution.<br /><br />Otherwise, it is a "week true" statement, but still NOT a false statement.<br /><br />So, in my opinion, you can BY NO MEANS score it as incorrect, that would be an undeserved punishment for those that not only realised it as being logically correct <br />(by the truth table of the boolean implication operation), but also objected on the fact<br />that it was not the "strongest" statement that can be derived from the clues.<br /><br />The quiz was already rated as Advanced, so I think you have nothing to change.<br /><br />In the worst case, you can credit everyone with a correct choice, though, you can never know<br />what was the reason for which those that marked it as incorrect have made their choice this way.<br /><br />May they have a bonus because of the ambiguity, but those that made a strong and correct rationing ( even more correct than was stated in the answers themselves ) cannot be punished,<br />that would be completely unfair.<br /><br />Thanks a lot & Best Regards,<br />Iudith MentzelAnonymousnoreply@blogger.com