Give me a ticket for an aeroplane

[austin_dern]

Oh, some fresh nuggets of data-mining gold. One of my friends from grad school went into this field for, I believe, American Airlines. I should ask him to go kick the United computer. In today's e-mail:

Subject: Enjoy an unforgettable week in Singapore with United
Singapore— truly a city like no other. A bridge between the East and West, Singapore is a vibrant melting pot of ideas, cultures, peoples and cuisine. Your visit is sure to leave you enriched, recharged and craving for more.

It offers truly marvelous fares for flying, between 15 October and 8 December, from Chicago, Los Angeles, Denver, or Washington to Singapore. They've got me perfectly targeted, except starting from the wrong continent, flying the wrong days, and coming from cities I have never flown to. Washington and Chicago I've visited by car; Chicago, Los Angeles, and Denver I've flown through.

In midterm grading carnage, two students (of 134) got three of the eight true/false questions right. Worst score was 21; several had 100's. The mean was 75.8, standard deviation 14.1, so I guess the test was just about right. An elevator door was slow in opening; another balked while halfway open. I don't explain it; I just report it. Also somehow an RPI Alumni in Singapore group found me.

Trivia: Dave Barry's son Rob was born on 8 October. Source: Dave Barry Slept Here, Dave Barry.

Currently Reading: The Halfling and other stories, Leigh Brackett.

Comments

[orv.livejournal.com]

Well, hey. There'd be no point in offering discounts on flights there was actual demand for, would there?

[austin-dern.livejournal.com]

I don't know -- if I spent US$350 on a plane flight it might be United's only working capital this month.

[bunny-hugger.livejournal.com]

On the logic midterm I just graded, two people out of 23 got all five of the true/false questions wrong, and several people got four of them wrong. This happens every time. It's because I can lecture on it until I'm blue in the face, but some people can't understand the concept of logical validity.

Me: "A valid argument is one in which if the premises are true, the conclusion must be true." [Followed by repeating at least a dozen times that this doesn't mean that the specific premises and conclusion of the actual argument under consideration are true.]

Them: [writing in their notes] "Valid = true premises and true conclusion."

Me: "An invalid argument is one in which it is possible for the premises to be true and the conclusion false." [Followed by strenuously insisting that this doesn't mean that the specific premises of any given invalid argument actually are true, or that the conclusion is always false. Examples are provided to head off this misunderstanding.]

Them: [writing in their notes] "Invalid = true premises and false conclusion."

I'm sure you can imagine how such misunderstandings could lead someone to get all the T/F questions wrong.

[argon-centaur.livejournal.com]

So how do you determine if the premises are true? If the premise is "If 2 + 2=4 and 4 + 4=8,then 8 + 8=32" could be considered true?

[mwmiller.livejournal.com]

I think the sort of logic under discussion here is of the sort
“If Joe is a human, and all humans wear hats, then Joe wears a hat.” The first condition (“Joe is a human”) may or may not be true; the second condition (“all humans wear hats”) probably is not; but if both conditions were true, then it follows that “Joe wears a hat” would be true: it's logically valid.

On the other hand, consider the statement “If Joe is a human, and Joe wears a hat, then all humans wear hats.” This statement is not logically valid, because if the two conditions (“Joe is a human” and “Joe wears a hat”) are true, Joe would still only be one example of a human and only one example of a hat-wearer.

[austin-dern.livejournal.com]

That's logical validity in a nutshell. My quick rule of thumb is if you can replace all the nouns in an argument with placeholder letters, and come out with something that's still clearly true, then you had a valid argument to start with. ``If all A are B, and C is an A, then C is B'' would be the argument above, with ``A'' in place of ``all men'', ``B'' in place of ``hat-wearers,'' and ``C'' in place of ``Joe''. (There's surely examples in which this goes wrong, but it's a usually reliable starting point.)

Soundness is whether the argument happens to be true ... for example, ``If Samuel Tilden got more electoral votes in 1876, then he would have been president after Grant'' is a valid argument -- you can't have the premise true without the conclusion also being true¹ -- but it so happens to be unsound, because Tilden didn't get more electoral votes.

[¹] And some other assumptions, such as that Grant and Tilden don't die before 4 March 1877 and the like, but you know what I mean.

[austin-dern.livejournal.com]

Testing whether the premises happen to be true, I think, plunges us into the question of how we know whether anything's true. I'm fine with starting from a set of axioms assumed to be true without reference to whether a premise is objectively true ... on the question of how to say whether the premise in an argument is true I'll defer happily to the philosophy Ph.D.

[austin-dern.livejournal.com]

Ow ... I always feel bad for students who do worse than random guessing. That may be part of why I tend to avoid true/false or multiple choice questions, other than I just have to think up more questions to ask for those sections.

I don't remember how I handled the validity-versus-soundness problem when I taught a freshman mathematical logic course back at Saint Rose ... I might have avoided it altogether, and concentrated instead just on the different types of syllogism argument.