From: RoyMayeda@aol.com
Date: Sun Oct 01 2000 - 10:17:18 PDT
From: RoyMayeda@aol.com Message-ID: <91.13f42a2.2708cb9e@aol.com> Date: Sun, 1 Oct 2000 13:17:18 EDT Subject: Re: Sig Figs
Neil -
Electronic balances are "WYSIWYG" (to a point) but you still have to contend
with sig figs during calculations, as there is still uncertainty in the
measurement. The uncertainty is due to the limits of precision of the
balance (nearest 0.0001 g, etc.).
Marc -
Yes, the convention of rounding numbers up when odd and just truncating the
number if even is arbitrary, but it does have a reason. Beginning students
are taught to round "down" if 0-4 are to the right of the place value being
rounded and to round "up" if 5-9 are found. If we assume that rounding a 0
"down" has no significant effect on the value reported, then we only decrease
the value if followed by 1-4 (4 possible digits). We would increase the
value if followed by 5-9 (5 possible digits). Statistically, this skews a
set of values being rounded so that they are too large. Rounding "up" only
on odd numbers and "down" only on even numbers (5 possible digits each) evens
the process out. The convention itself is not arbitrary, but the decision
regarding which half of the values increases and which half decreases was
arbitrary.
Roy Mayeda
Valley HS, Sacramento
RoyMayeda@aol.com
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