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On Fri, 10 Apr 1998, Cory J. Briggs wrote: > I received from you the following post. Although I do not take > issue with the substance of your argument, I do take issue with its form and > the ultimate conclusion. Here's why: <snip> Yeah, about two seconds after I hit the send key on that one I realized I should have put in a note on this. It's not programming, and it's not logic, it's some dive guy who wrote this question. We know that he was grammatically using "or" as a connective, which should probably have been "and", or better, since the obvious intention was that you won't use O2 both ways at the same time, ", alternately" would have made the question clearer without tempting students to apply boolean logic. So, how do we know TDI aren't a bunch of logicians (aside from the obvious :)? Since nobody is going to argue with O2 increasing safety, (the first part before the "or"), the logician's answer to the question would be TRUE. But TDI says the answer is FALSE, so assuming TDI people think O2 can be used to increase safety (a safe bet), they must have been using "or" in the grammatical context noted above. Which is what I would have assumed if I'd been taking the test, knowing full well it was a dive test, not a logic test. So the grammatical "or" is effectively a logical "and" in this case - which I should have fully explained, but this is really long-winded, and everyone would be nodding off, like now. -Will > On Thu, 9 Apr 1998, Tom Mount wrote: > > > The statement was about a bulhman model I happened to agree with the answer > > Trout gave and showed the list why, by running bulhman model tables. > > Tom > > Tom, let's go back and parse the question, since it's clear > the question was lost among all the posturing in this thread: > > 7. Oxygen can be employed to increase safety regarding DCS or it > can be used to shorten decompression time by permitting the diver to > conduct the 10fsw stop at 20fsw. > > True/False. > > OK first, "or" makes this two statements, making the entire question > false if either individual statement is false. What we > get is: > > [1] "Oxygen can be employed to increase safety regarding DCS" > > Clearly, this is true. > > [2] "it can be used to shorten decompression time by permitting the diver to > conduct the 10fsw stop at 20fsw." > > The statement "it can be used to shorten decompression time" > > is also obviously true, which is what I think you were > getting at with your deco examples. Again, nobody is > going to argue with that part - obviously O2 can be > used for accellerated decompression. > > The problem comes with the next part; "by permitting the diver to > conduct the 10fsw stop at 20fsw" which describes HOW it is > that it can be used to shorten deco. > > IANTD uses Bulhmann tables in the manuals, and promotes > Buhlmann-based deco software packages. > I assume TDI does as well. > > The simple fact is that if you are using Buhlmann, > and you are breathing pure O2, conducting the 10fsw stop > at 20fsw will not make one second of difference in > your hang time. > > And that makes the second part false, which makes > the entire statement false - which makes the answer "FALSE". > > [Cory resumes here.] Question no. 7 is a disjunct, to use the logician's > term. As such, it is true if EITHER of the statements contained therein is > true. For instance, "either Madonna is a female or else she holds the > record for the deepest scuba dive" is true, because the first part of the > disjunct--that is, "Madonna is a female"--is true. > > Will, in your analysis of Question no. 7, the answer is TRUE because, as you > yourself point out, the first statement regarding the use of oxygen to > increase safety against DCS is true. It matters not that the second > statement is false, in purely logical terms, because this is a disjunctive > question. Had it been a conjunct--i.e., "and"--you certainly would be correct. > > Again, I must reiterate that I do not take issue with your > substantive analysis. I am only pointing out one of the formal errors in > your analysis. > > Respectfully submitted, > > Cory J. Briggs, NAUI no. 14693L > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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