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    SubjectRe: temperature standard - global config option?
    On Fri, Jun 08, 2001 at 05:16:39PM -0400, Albert D. Cahalan wrote:

    > The bits are free; the API is hard to change.
    > Sensors might get better, at least on high-end systems.
    > Rounding gives a constant 0.15 degree error.
    > Only the truly stupid would assume accuracy from decimal places.
    > Again, the bits are free; the API is hard to change.

    Twice a year I'm a judge at science fairs. Once at the local
    level and once at the state level. I generally judge on the senior
    level in the physics category. All too often I have a hard time even
    convincing some of my fellow judges.

    Each year there is at least one project where some student has
    used "fancy scientific equipment" to make measurements of impressive
    precision and beautiful results. Till you look closer and you find that
    their standard deviation is as large as their averages and their raw
    test results are all over the map. With 5 or more decimal places of
    precision, you find that their sample sizes and proceedures don't even
    support one or two decimal places, if they are lucky.

    If it were not for the fact that I don't think they are really
    that good at it, I would give them an award for "if you can't dazzle them
    with brilliance, baffle them with bullshit". Unfortunately, they honestly
    don't KNOW the difference between precision and accuracy. We often
    judge between a half a dozen and a dozen exhibits. This comes up
    every year and gets written up in comments every year. Of course, you
    can't be harse in judging these things and most of them really do make a
    legitimate effort, but it is difficult to tactfully explain to someone
    why their elaborate and extremely detailed results amount to utter
    jibberish. (To the smartasses who are about to fire off the obligatory
    smart remarks: Trust me, I am much more tactful with those students
    than I am on this list... Maybe I shouldn't be. Read that either way.)

    What's more apalling is that their teachers did not catch this
    and I have to point out the fatal flaws to a lot of my co-judges who
    were impressed with the scientific prowess of these individuals.

    No... The average person, NO, the vast majority of people,
    DO assume accuracy from decimal places and honestly do not know the
    difference between precision and accuracy. I've had comments on this
    thread in private E-Mail the reinforce this impression.

    Yes, bits are free, sort of... That's why an extra decimal
    place is "ok". Keeping precision within an order of magnitude of
    accuracy is within the realm of reasonable. Running out to two decimal
    places for this particular application is just silly. If it were for
    calibrated lab equipment, fine. But not for CPU temperatures.

    Yes, APIs are difficult to change. But can you honestly say
    that, even if we magically get off the shelf economical temperature sensors
    that are two orders of magnitude more accurate (without need of constant
    tracible recalibration - these things DO drift), that this level of
    precision would have any real meaning at all? I would expect the
    CPU temperature to vary by a few hundreths of a degree just by how
    many people were sweating in the cube next to me.

    Even the rounding error vis-a-vis the .15 is silly and irrelevant!
    If the sensor is +- 1 degree, you can't even measure the rounding error,
    even if you HAVE two decimal places. With that degree of accuracy, you
    are no better off than 273 with no decimal places. Worrying about rounding
    error on .15 when the accuracy is in the units is exactly the kind of
    misinformed false precision that I worry about. You actually though that
    the .15 was significant enough to worry about round error when, in fact,
    it will be impossible to measure with the equipment available in the
    environment of discourse.

    > One might provide other numbers to specify accuracy and precision.

    Now... That I can agree with and it would make absolute sense.
    Especially if we were discussing lab grade or scientific grade measure
    equipment and measurements. In fact, that would be a requirement for
    any validity to be attached to measurements of that level of precision.
    But that's not what we are talking about here, is it? We're not talking
    about a lab grade instrumentation API here, are we? If we are, then
    everything changes.

    Mike
    --
    Michael H. Warfield | (770) 985-6132 | mhw@WittsEnd.com
    (The Mad Wizard) | (678) 463-0932 | http://www.wittsend.com/mhw/
    NIC whois: MHW9 | An optimist believes we live in the best of all
    PGP Key: 0xDF1DD471 | possible worlds. A pessimist is sure of it!

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