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Suppose the position of an object is at time . Suppose you want to graph this data point. How do you do it?

Of course we could simply graph the point (1.26 m, 4.2 s), which
represents our best estimate for the point, but actually what we have
is *not a point*! The position could reasonably be anywhere
between 1.22 m and 1.30 m, and the time could reasonably be anywhere
between 4.0 s and 4.4 s. Your "data point" is actually a "data
rectangle"!

Instead
of indicating the precision of a data point using a rectangle, it is
common practice to use "error bars" to indicate precision. (I suppose
coloring in all those big rectangles doesn't seem like a good use of
time to physicists, and it would certainly get confusing with
closely-packed points!) Error bars are simple to draw, and most
software packages designed for scientific graphing, such as *Graphical
Analysis*^{TM} and *Science
Workshop*^{TM}, will do them for you quite easily.

last update July 14, 2000 by JL Stanbrough