Surprise Quiz

[Emporion]

The students are assuming too much in their premise. How do they know " the quiz doesn't happen by Thursday, it'll be obvious the quiz is on Friday"? That logic will work with every day and they will still be wrong.

[lilphil1989]

Adrian, I think now would be a good time for a hint!

[Cinjin]

What's the flaw in the students' thinking?

The "Friday Theory" that the students came up with is a causatum. In order for the theory to work certain factors must be made to come into cause. It only holds true if the professor chooses not to give the quiz until Thursday. And since the forward nature of time prevents one from utilizing this theory, it is impossible to use as a working solution.

Also, Min is right - the professor's a dick.

[Tiberius]

Most of you (except the guys holding onto the "prof prick theory") have got parts of it, although to be fair, there is no clear answer to this problem in mathematics yet.

What is clear though is that parts of the problem are a paradox (well done to those people who figured that out). There is also a big error in the students conclusion, caused in part by the paradox.

Firstly, the paradox:

The professor told the students that there would be a surprise test the next week, so it could either be on Monday, Tuesday, Wednesday, Thursday, or Friday. It can't be on Friday because on Thursday evening the students would know the test had to be on Friday (the only day left), and therefore wouldn't be a surprise. It can't be on Thursday for the same reason, since on Wednesday evening the students would know it had to be on Thursday (since it can't be on Friday). This argument applies for each preceding day, until we reach the conclusion that the test cannot be on any day.

Of course, the paradox is that the test seemingly can't be on any day without being a surprise test, and yet this is clearly untrue, since the professor can surprise the test on his students on any day.

The error in the students reasoning lies in their conclusion; because of the paradox, they conclude that the test cannot happen on any day. However, this is in stark contradiction to what the professor told them (that there would be a test at some point next week). Also, the professor told them that he would cancel the test if the students were able to guess what day it would be on; however, they did not do this. They deduced that the test could not be on any day, and as such, did not expect it on any day. The professor could then easily schedule the test for any day (even Friday) and it would be a surprise.

It should be noted that there are many objections to the whole problem in the first place, hence why it is currently "unsolved". My explanation is but one of many possibilities (others are listed here).

[Cinjin]

Most of you (except the guys holding onto the "prof prick theory") have got parts of it, although to be fair, there is no clear answer to this problem in mathematics yet.

What is clear though is that parts of the problem are a paradox (well done to those people who figured that out). There is also a big error in the students conclusion, caused in part by the paradox.

Firstly, the paradox:

The professor told the students that there would be a surprise test the next week, so it could either be on Monday, Tuesday, Wednesday, Thursday, or Friday. It can't be on Friday because on Thursday evening the students would know the test had to be on Friday (the only day left), and therefore wouldn't be a surprise. It can't be on Thursday for the same reason, since on Wednesday evening the students would know it had to be on Thursday (since it can't be on Friday). This argument applies for each preceding day, until we reach the conclusion that the test cannot be on any day.

Of course, the paradox is that the test seemingly can't be on any day without being a surprise test, and yet this is clearly untrue, since the professor can surprise the test on his students on any day.

The error in the students reasoning lies in their conclusion; because of the paradox, they conclude that the test cannot happen on any day. However, this is in stark contradiction to what the professor told them (that there would be a test at some point next week). Also, the professor told them that he would cancel the test if the students were able to guess what day it would be on; however, they did not do this. They deduced that the test could not be on any day, and as such, did not expect it on any day. The professor could then easily schedule the test for any day (even Friday) and it would be a surprise.

It should be noted that there are many objections to the whole problem in the first place, hence why it is currently "unsolved". My explanation is but one of many possibilities (others are listed here.

Just a little nitpick here:

You did not ask us to answer the question that the professor posed. I wouldn't have even wasted my time with such stupidity ... thus my remark about the professor being a dick.
YOUR question specifically was:

What's the flaw in the students' thinking?

I answered it as clearly as that question can possbily be answered. The truth is, the whole scenario is ridiculous and I wish I wasn't STILL wasting my time on it.

[Tiberius]

Just a little nitpick here:

You did not ask us to answer the question that the professor posed. I wouldn't have even wasted my time with such stupidity ... thus my remark about the professor being a dick.

I don't get how that is nitpicking? I explained what the flaw in the students thinking was; in order to explain it, I needed to first explain the paradox behind the problem.

YOUR question specifically was:

What's the flaw in the students' thinking?

I answered it as clearly as that question can possbily be answered. The truth is, the whole scenario is ridiculous and I wish I wasn't STILL wasting my time on it.

No, you didn't answer it clearly at all. The "Friday Theory" as you call it is perfectly logical; it just forms a paradox because of the usage of the word "surprise" and other factors (I suggest you read the Wikipedia page I linked to for a full analysis of the problem).

[Cinjin]

YOUR question specifically was:

What's the flaw in the students' thinking?

I answered it as clearly as that question can possbily be answered. The truth is, the whole scenario is ridiculous and I wish I wasn't STILL wasting my time on it.

No, you didn't answer it clearly at all. The "Friday Theory" as you call it is perfectly logical; it just forms a paradox because of the usage of the word "surprise" and other factors (I suggest you read the Wikipedia page I linked to for a full analysis of the problem).

Jesus christ seriously?! - it's not even a solvable problem - it's just a silly brain teaser that a "way cool" junior-high teacher asks the 7th graders during studyhall!

Now this will be the LAST time I stop by this thread, but you can't call the "Friday Theory" perfectly logical if it's plagued with paradoxes -- that's just ridiculous. And since that IS the case, yes, I DID answer the question as clearly as can possibly be answered. Read your question aloud and than read my original answer. There is NO better concise answer for an unsolvable problem. What, am I having a battle of wits with an unarmed man here?! It's psuedo-intellectual. It's bull shit.

Definition of concise: brief in form but comprehensive in scope (talking in circles really shouldn't be considered strong debate skills) and Wikipedia .. REALLY?!




my apologies to any friends of adrian .... but damn I nearly gave the same god damn answer as he did!

[Rayaan]

The error in the students reasoning lies in their conclusion; because of the paradox, they conclude that the test cannot happen on any day. However, this is in stark contradiction to what the professor told them (that there would be a test at some point next week). Also, the professor told them that he would cancel the test if the students were able to guess what day it would be on; however, they did not do this. They deduced that the test could not be on any day, and as such, did not expect it on any day. The professor could then easily schedule the test for any day (even Friday) and it would be a surprise.

So I got that much of it right.

This was pretty easy actually. I knew that just by thinking that the quiz would be cancelled, it can be given to them on any day since it's a surprise quiz.

[reverendjeremiah]

prof prick theory

Well played Adrian, it is true that we are assuming the professor is a prick.

..BUT..

You are assuming that the students WANT to get out of doing the quiz.

what if the students are screwing up on purpose because they OBVIOUSLY need to take this quiz?

LMFAO...you do have a sense of humor dont you?

[Emporion]

Most of you (except the guys holding onto the "prof prick theory") have got parts of it, although to be fair, there is no clear answer to this problem in mathematics yet.

What is clear though is that parts of the problem are a paradox (well done to those people who figured that out). There is also a big error in the students conclusion, caused in part by the paradox.

Firstly, the paradox:

The professor told the students that there would be a surprise test the next week, so it could either be on Monday, Tuesday, Wednesday, Thursday, or Friday. It can't be on Friday because on Thursday evening the students would know the test had to be on Friday (the only day left), and therefore wouldn't be a surprise. It can't be on Thursday for the same reason, since on Wednesday evening the students would know it had to be on Thursday (since it can't be on Friday). This argument applies for each preceding day, until we reach the conclusion that the test cannot be on any day.

Of course, the paradox is that the test seemingly can't be on any day without being a surprise test, and yet this is clearly untrue, since the professor can surprise the test on his students on any day.

The error in the students reasoning lies in their conclusion; because of the paradox, they conclude that the test cannot happen on any day. However, this is in stark contradiction to what the professor told them (that there would be a test at some point next week). Also, the professor told them that he would cancel the test if the students were able to guess what day it would be on; however, they did not do this. They deduced that the test could not be on any day, and as such, did not expect it on any day. The professor could then easily schedule the test for any day (even Friday) and it would be a surprise.

It should be noted that there are many objections to the whole problem in the first place, hence why it is currently "unsolved". My explanation is but one of many possibilities (others are listed here).

That was a piece of cake after I quickly realzed that the students were using baseless assumptions for their conclusion "There is no quiz this week. I think the students deserved the test after that epic logical failure. Do I get a cookie for the right answer(and paradox explanation)?