Re: [Phys-l] 9.80 vs. 9.81

["Michael Edmiston" <edmiston@bluffton.edu>]

It has been my intent to tell students that the USGS values we have on 
record for several spots in Bluffton are "measured" and "published" values. 
The publication has an introductory section that states exactly how the 
measurements were made and what steps were taken to assure that the accuracy 
stated is figured correctly.  I can't remember if I might have called it an 
"accepted" value on some occasions.

There are situations in which "accepted" value can be quite legitimately 
used, and the USGS data may be one of those.  The g values in my area have 
been measured more than once and published by USGS.  However, USGS personnel 
did not make the measurements.  They often subcontract this type of work to 
various engineering firms.  The engineering firms have to make the 
measurements in a particular way (or sometimes choose one of several ways) 
that is approved by USGS.  After submitting the data to USGS, analysts there 
determine whether to accept the data as meeting their standards, or making 
the subcontractor repeat some of the measurements.  Once the USGS is 
satisfied, and they publish the data, it seems reasonable to me to say the 
values are accepted values, because the government agency responsible for 
such measurements has put their "stamp of approval" on the measurements. 
John Clement is certainly correct that this does not mean it is correct, not 
that it won't change.

I think there are quite a few measurements made these days that go through a 
certification procedure and then become accepted.  Air-quality monitoring 
and water-quality monitoring are a couple important examples in my area and 
in many areas.  The official ozone level for my county is an accepted value. 
Each annual value is is accepted by both the Ohio-EPA and the US-EPA based 
upon measurements that are performed in a specified manner and include audit 
trails of instrument calibrations, etc.   Once these annual numbers are 
"accepted", a 3-year rolling average is calculated.  The currently-accepted 
overall value is the average of the accepted annual values for 2007, 2006, 
and 2005.  This 3-yr average value becomes the legal basis for whether we 
are in attainment or out-of-attainment with the US Clean Air Act with regard 
to ozone.  The difference can mean millions of dollars (in fact billions in 
my county) in terms of whether existing industries can continue to operate, 
or expand, or new industries can come into the area.  This is particularly 
complicated right now because the old ozone limit was 0.084 ppm and the new 
USA limit that just took effect is 0.075 ppm.  The currently-accepted value 
for my county is 0.078 ppm.  Even though that number could be wrong, it went 
through the proper certification channels and is the accepted value. 
Therefore, with the recent change in standards we just slipped from slightly 
within attainment to slightly out-of-attainment.  Unless we can achieve some 
reduction in the accepted value, we will see significant negative economic 
impact from this.  Of course the EPA maintains we will see a greater 
positive health benefit because of the new standard.

I think it is good that John Clement pointed out that there can be a 
difference between measured values, published values, and accepted values. 
These descriptors are not synonymous.  I think many people, especially 
students, are unaware that many things indeed are measured and then become 
accepted through a particular chain of processing by some entity authorized 
to declare acceptance.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
1 University Drive
Bluffton, OH 45817
419.358.3270
edmiston@bluffton.edu


--------------------------------------------------
From: "John Clement" <clement@hal-pc.org>
Sent: Sunday, April 20, 2008 2:43 PM
To: "'Forum for Physics Educators'" <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] 9.80 vs. 9.81

> This is of course good advice.  I would call the USGS value a standard, or
> published value rather than an accepted value.  Who is it accepted by?
> Standard implies that someone or some group decided that the value was to 
> be
> used as a standard, but does not imply that it is the gospel truth.  I 
> tend
> to see red when the phrase accepted value is used.  And of course it is
> possible for the value to change with time.
>
> John M. Clement
> Houston, TX