I love people who think logically - except when they expose my illogic

Received this via email today:
I have just found the PL/SQL Challenge and I am eager to get started. Under Instructions on the Quiz Introduction page is something to which I would like to call your attention. 
"For most quizzes, however, it is possible that more than one choice is correct, that all choices are correct, or that none of the choices are correct. You must check at least one box from those offered before you can submit your answer." 
How might one check a box and then submit if none of the choices are correct?
On first reading, I groaned. Really? Did I really leave a big hole like that in our quiz-taking process or - not quite as alarming - in my text? Is that a contradiction?

No! No! No!

There is an explanation which leaves me firmly on the right side of Logic.

Can you see what it must be? 

I will post this first as a small logic puzzle via Twitter, then I will update this post in a day or two with my answer.

A day goes by.

Another day goes by.

Marcus solves the puzzle (see comments).

Here's the answer:

Nowhere in the text do I say that a "box" on the page must correlate to one of the choices. In fact, there is a box (a selection you can make) that is explicitly....

So that's the solution to the logic puzzle.

But Chris also makes a great point in the comments below that an explanation should not be needed for explanatory text. :-) So I am going to fix that text.

And that makes for a nice bonus to this post - I improve my application!


  1. There are checkboxes for the choices and one checkbox for "none is correct". Therefore not all boxes "from those offered" are connected to a choice.
    So if no choice is correct you can logically correct check the "none is correct" box.

  2. If all answer are wrong then you need to chek them all, question will be asked like chek all wrong etc. Simple play of word's. From PL/SQL side you have problem counting correct answers, in this case you need to do negation or even compare to null

  3. Presumably, "boxes" doesn't necessarily mean the same thing as "choices." You might have a question offering choices A and B, and boxes for "A only", "B only", "A and B" and "Neither A nor B".

    However, whilst you may be convinced your wording is logical (whether or not my explanation is right) it fails on the grounds of clarity. We shouldn't need to solve a logic puzzle to understand what you mean.

  4. You got it, Marcus! Not all boxes are connected to a choice. As I will now update in my post, there is a selection for "No choice is correct."

    Chris, I am not sure if you looked at the quiz page, but I think it is entirely clear from the UI - however you raise a very good point. Our text should not be confusing in the least. I will fix that.

  5. I am not sure did i submit comment.... comment was what will happen if i answer one from four choice? what will be my % of correct answers?

    1. If you check all boxes? Well, generally, our quizzes are NOT "all or nothing" (though some are). So you receive credit for the selections you made correctly, even if you also checked one or more boxes for incorrect choices.

    2. i know, that is why i am asking, lets say: we have 5 chk a,b,c,d and e ( e as all are wrong). i chek a and leave b,c,d,e empty, what will be my score 75% or 60% :)

    3. 80%. You got four choices right, and 1 wrong. Assuming I understood you: 5 choices, all incorrect, choose one as correct.

    4. ah let me try again regroup my thought
      a) answer1
      b) answer2
      c) answer3
      d) answer4
      e)all wrong
      ( lets say e is correct)
      i mark only a(answer) as correct
      in this case what is % of correct answers?

    5. You get 75% correct. "All wrong" or "No choice is correct" is not a "choice" that is counted in the scoring. It is merely a quick and easy way to let the player turn off all choices.

  6. This comment has been removed by the author.

  7. The piece that states "...or none of the answer choices is correct" contradicts the answer choice "no choice is correct" because that last choice is correct. Unless that last box is not a choice

    1. That's right it is NOT a choice. It is a "meta-choice" that disables all checked choices.


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