Surprise Test Paradox

[nitrocan]

Some of you might have heard of this as the "Unexpected Hanging Paradox" too, but here it goes:

On a friday afternoon, a teacher announces that the students will have a surprise test someday next week. At the weekend, one student thinks "If the exam were to be on friday and if we still didn't have the exam on thursday, we'll easily know that the exam will be on friday. So it won't be a surprise." Then he thinks again "If there can't be an exam on friday, then thursday will be the last day to have an exam and if we still haven't had the exam on wednesday, we'll know it's on thursday and it won't be a surprise.". He keeps doing this and concludes that they can't have a test next week. Thursday comes and they have a test, and the students are obviously surprised.

What's the flaw in this logic? Post your thoughts.

Spoiler

There isn't actually a really explanatory answer for this. lol

 

[krazedkat]

Since the student concludes that they CAN'T it is a suprise to them that they DID... Pretty obvious...

 

[nitrocan]

Since the student concludes that they CAN'T it is a suprise to them that they DID... Pretty obvious...

No, but where's the FLAW in the logic?

 

[Bryan]

Even when you do have a surprise test, at some point you gain knowledge of when it's going to occur, at this point it's no longer a surprise. Now, does it matter if this duration is 1 minute or 1 day? The point is, beforehand you did not know when the event would occur, and now you do.

 

[PatrickJameson]

Why can't there be an exam on Friday?

 

[Stefan]

http://en.wikipedia.org/wiki/Unexpected_hanging_paradox

 

[PatrickJameson]

http://en.wikipedia.org/wiki/Unexpected_hanging_paradox

Ah, I understand now.

 

[Holger]

Well it isn't a surprice since it is announced...

And i feel there is to many "negative" argumentation in the statement.