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Step 4: Determine Accuracy
Objective:
Determine the closeness of agreement between an experimental
measurement of a characteristic and the true value of that characteristic.
Process:
Either choose:
a. one sample standard from the middle of the expected
measurement range.
or
b. several sample standards from the low end, middle, and high end
of the expected measurement range.
If sample standards are not available, use production units from the
expected measurement range. Have the samples measured 15
times on a measurement system with a known bias (calibration lab).
Compute the average of the 15 readings. Use this average as the
“reference value”.
Measure the sample standard 15 to 25 times in as short a period of
time as possible using the same operator, same equipment, and
same set-up to obtain the data.
Compute the average of the readings,
X
.
Compute the bias using the following equation:
bias
=
average
-
reference value
