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# Re: [Phys-L] rounding

• From: "Christopher M. Gould" <gould@usc.edu>
• Date: Fri, 24 Aug 2012 17:51:30 -0700 (PDT)

Date: Fri, 24 Aug 2012 16:44:23 -0400
From: Robert Cohen <Robert.Cohen@po-box.esu.edu>
To: Phys-L@Phys-L.org
Subject: [Phys-L] rounding
> As background, the Pennsylvania Department of Education has
> mandated that all candidates for teacher certification must
> have a 3.0 GPA. This has naturally led me to question
> whether the use of one zero was intentional. Our
> institution, for example, used to report GPA to the
> hundredths and, as such, concluded that a 2.99 GPA was not
> sufficient....

You're confusing the exact value of a number with its representation,
and confusing a physics issue (an experimental value) with a policy
issue (setting a threshold).

When the Pennsylvania Department of Education says "3.0" it does not
mean "something within experimental error of 3.0." They mean the exact
number 3. They themselves recognize that setting their threshold is
arbitrary, but not to set a threshold is a prescription for inaction.
Witness their clarification to you:

> Program providers may not round up the final GPA to a 3.0 for
> the purpose of recommending a candidate for certification.
> The cutoff has to be applied at some point. If the cutoff is
> not 3.0 then it becomes impossible to draw the rounding up
> line.

The second sentence could have been written better, but the idea is
clear: they determined that there must be _some_ cutoff, and this is
just what they picked. It could just as well have been any other
number.

A person's GPA is an exactly calculable number which can be compared to
the exact number 3 with a definite answer, though as others have
commented, its exact value is somewhat meaningless without context.
However, to force consideration of context would erase the benefit to
the policy makers of the cutoff.

This isn't a physics issue.

_________________
Christopher M. Gould 213-740-1101 Dept. of Physics & Astronomy
gould@usc.edu Univ. of Southern California
http://physics.usc.edu/~gould/ Los Angeles, CA 90089-0484