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05 May 2008
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Accuracy vs. Precision

If you've ever taken a science class, you've endured at least one discussion of this subject.  If you embody nerdish tendencies, you might even remember the distinction instead of using the words interchangeably.

When referring to a fact or a measurement, its accuracy can be considered how closely it is related to the truth.  For example, if you're giving someone directions and say the destination is 14 miles from a certain intersection, this non-precise datum would tell the motorist to begin his lookout at 13.5 miles and maybe begin to worry at 14.5.  If you told him the destination was at 12.1 miles, a number more precise by a factor of 10 (a "decimal order of magnitude"), he would need a much shorter attention span.  However if your precise datum (12.1 miles) weren't accurate and it was truly about 14 miles, the added precision would be of little value.

The reverse can also be true.  Let's say that you just happen to have purchased a new gas stove top about two and a half years ago, and you wish to use it to replace an old electric stove, one with defective burners.  If the two stoves aren't exactly the same size, (which they are not), you don't really need an accurate measurement of the size of either stove.  Rather you need a precise measurement of the difference between the two so you can make a shim or perhaps cut out a small additional area to replace the old stove with the new.  (You also don't need completely new counter tops or a remodeled kitchen or a new dishwasher and microwave, but what do I, a card-carrying guy-person, know about kitchens anyway?)

Where's the Newspaper?

Which brings me to the real subject of this blogitem, which is newspaper delivery.  If you have been reading my blog for a while, you will have noticed that I often refer to items in the Wall Street Journal.  Just today, for example, I have added polyethylene terephthalate as the "chemical of the day" since this is the first time I have seen it spelled out in the Journal.  To have read about this chemical, I must have obtained a copy of the Journal.  I accomplish this daily by walking to the end of the driveway and picking it up.  My driveway is a conventional one.  It is somewhat wider than a car, and has dirt, leaves, rocks, and other suburban detritus to either side.  In contrast to its surroundings, it is black.  It is well-fixed in its geospatial coordinates.  All my vehicular visitors inevitably can negotiate it, and its contrast should make it an excellent target.

Except, it would seem, for the newspaper delivery person.  I assume he (or she) is a professional deliverer, i.e., is getting paid, probably through intermediaries, by the stately Wall Street Journal.  Further evidence of her (or his) professional character is the precision with which the paper is delivered every day.

Note that the paper is to the right of the driveway, where it requires groveling in the leaves to retrieve it.  It is in this same location every day.  If that isn't professional-grade precision, I don't know what is!

Behold now a demonstration of accuracy.  Recall that I asserted that the driveway is of a reasonable width.  In the simulation below, you will see an example of an accurate delivery.  Any location on the driveway would be considered accurate, even if precision were sacrificed.

Observe how small the paper is with respect to the driveway target?  Don't you think that a delivery professional would take pride in his (or her) accuracy and precision, especially since the target area is so much larger than the one that is customarily (and precisely) hit?  I thought so, too, until I realized that I am being deliberately slighted.  Could it be that the deliverer is simultaneously demonstrating notable precision while deliberately eschewing accuracy for the purpose of delivering a message to me?  Tragically, it is difficult to deliver a coherent message only by newspaper placement.  Far better to get it in the center of the driveway and scribble a note on the wrapper.  But, clearly, that is not to be.

I could call the deliverer to "complain" but I try not to be a whiner, don't mind the occasional grovel, and in any event haven't been able to obtain the telephone number or email address.  Alternatively, I could log the exact location and orientation of the paper every day and try to deduce the message from the angle and, perhaps, the deviation in location from an arbitrary marker.  Or even, with enough ambition, find a way to turn the daily positional vicissitudes into a Fourth of July party contest.  But I shan't.  Just minutes ago a truck delivered this year's mound of mulch.


NP:  "Home By The Sea" - Genesis

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