Calculation uncertainties
Everything that is calculated using measured quantities is subject to uncertainty. For
instance, there is uncertainty in the area of a floor computed from its length and breadth
measurements due to the uncertainties in those measurements. What is the magnitude
of the uncertainty in a multiplication or division calculation? Adding percents can be
utilized for multiplication or division if the measurements used in the computation
have minimal errors (a few percent or less). According to this method, the total of the
percent uncertainties in the items employed in the calculation represents the percent
uncertainty in a quantity computed by multiplication or division. For instance, the area
of a floor with an error of 3% is 12.0 m2 if its length is 4.00 m and its width is 3.00 m,
with uncertainties of 2% and 1%, respectively. (Since the size of the floor is given to a
tenth of a square meter, we round this to 0.4 m2 when expressed as an area, which is
0.36 m2 [].)
Calculation errors are a natural part of every outcome that comes from measured data.
This means that because of the constraints of the measurements used to make the
calculation, each computation—no matter how exact—carries some degree of
uncertainty. Take the relatively straightforward task of figuring out a floor's size, for
example. The length and breadth measurements have inherent uncertainties of their
own, so even with exact measurement, the final area computation will have some
uncertainty. This raises a recurrent question: in multiplication and division operations, how can we
assess the magnitude of this uncertainty? Fortunately, there is a workable solution
when the initial measurements have relatively small errors, usually a few percent or
less. We refer to this technique as the "method of adding percents." It suggests that the
percentage of uncertainty in a computed quantity is roughly equivalent to the total
percentage of uncertainty in each of the separate quantities that were employed in the
computation.
Let's go back to the floor area calculation example to help clarify this idea. Assume that
we measure the floor's length at 4.00 meters with a 2% margin of error and its breadth
at 3.00 meters with a 1% uncertainty. 12.0 square meters would be the computed area.
The uncertainty in the region would be 3% (2% + 1%), based on the addition approach.
This corresponds to a 0.36 square meter absolute uncertainty (3% of 12.0 square meters).
We would round this uncertainty to 0.4 square meters because the area is stated to the
nearest tenth of a square meter. As a result, we would specify 12.0 ± 0.4 square meters
as the floor's ultimate area.
A useful technique for measuring uncertainty in multiplication and division
calculations is the addition of percentages method. It offers a simple means of
evaluating the total uncertainty of a result with respect to the uncertainties of the
individual measurements. It's crucial to keep in mind that this approach is
approximative and works best when the uncertainties are minimal. More advanced
statistical methods could be needed to get a more accurate estimate of the uncertainty in
the estimated quantity when dealing with bigger uncertainties.
Calculation Uncertainties
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