Measurement Precision, Accuracy, and Error

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Measurement:
Precision, Accuracy, and Error

West Baton Rouge Parish Schools
Precision in Measurement
Precision
Precision is how close the
measured values are
to each other.
Accuracy in Measurement

Accuracy
Accuracy is how close a measured value is
to the actual (true) value.
Degree of Accuracy
Accuracy depends on the instrument you are measuring with.
But as a general rule:

The degree of accuracy is half a unit each side of the unit of
measure

measures in "1"s then                           measures in "2"s
any value between 6½                              then any value
and 7½ is                               between 7 and 9 is
measured as "7"                               measured as "8"
Error in Measurement
encompasses both the imprecision of data and its
inaccuracies
High Accuracy… Low Precision
High Precision … Low Accuracy
If we measure the length of a foot-ruler and get
values of

12.01 in, 12.00 in, 11.99 in, 12.00 in.

These numbers are precise enough for us to
believe that if we measure it again we would get
12.00+0.01 in.
These measurements are precise but necessarily
accurate.
The foot-ruler may actually be metric ruler of 30.0
cm long. Our measurement is precise but not
accurate.

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 views: 88 posted: 9/5/2010 language: English pages: 11