This concept of random and systematic errors is related to the precision and accuracy of measurements. Precision characterizes the system's probability of providing the same result every time a sample is measured (related to random error). Accuracy characterizes the system's ability to provide a mean close to the true value when a sample is measured many times (related to systematic error). We can determine the precision of a measurement instrument by making repeated measurements of the same sample and calculating the standard deviation of those measurements. However, we will not be able to correct any single measurement due to a low precision instrument. Simply stated, the effects of random uncertainties can be reduced by repeated measurement, but it is not possible to correct for random errors.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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PLTW Engineering
Activity 3.8 Precision and Accuracy of
Measurement
Introduction
This concept of random and systematic errors is related to the precision and accuracy
of measurements. Precision characterizes the system's probability of providing the
same result every time a sample is measured (related to random error). Accuracy
characterizes the system's ability to provide a mean close to the true value when a
sample is measured many times (related to systematic error). We can determine the
precision of a measurement instrument by making repeated measurements of the same
sample and calculating the standard deviation of those measurements. However, we
will not be able to correct any single measurement due to a low precision instrument.
Simply stated, the effects of random uncertainties can be reduced by repeated
measurement, but it is not possible to correct for random errors.
We can determine the accuracy of a measurement instrument by comparing the
experimental mean of a large number of measurements of a sample for which we know
the "true value" of the characteristic of the sample. A sample for which we know the
"true value" would be our calibration standard. We may also need to characterize the
accuracy of the measurement instrument by observing historical trends in the
distribution of measured values for the calibration standard (this allows for determining
the systematic error expected from environmental effects, etc.). The effects of
systematic uncertainties cannot be reduced by repeated measurements. The cause of
systematic errors may be known or unknown. If both the cause and the value of a
systematic error are known, it can be corrected for by "subtracting" the known deviation.
However, there will still remain a systematic uncertainty component associated with this
correction.
Equipment
• Engineering notebook
• Gauge block
Dial caliper
Transcribed Image Text:PLTW Engineering Activity 3.8 Precision and Accuracy of Measurement Introduction This concept of random and systematic errors is related to the precision and accuracy of measurements. Precision characterizes the system's probability of providing the same result every time a sample is measured (related to random error). Accuracy characterizes the system's ability to provide a mean close to the true value when a sample is measured many times (related to systematic error). We can determine the precision of a measurement instrument by making repeated measurements of the same sample and calculating the standard deviation of those measurements. However, we will not be able to correct any single measurement due to a low precision instrument. Simply stated, the effects of random uncertainties can be reduced by repeated measurement, but it is not possible to correct for random errors. We can determine the accuracy of a measurement instrument by comparing the experimental mean of a large number of measurements of a sample for which we know the "true value" of the characteristic of the sample. A sample for which we know the "true value" would be our calibration standard. We may also need to characterize the accuracy of the measurement instrument by observing historical trends in the distribution of measured values for the calibration standard (this allows for determining the systematic error expected from environmental effects, etc.). The effects of systematic uncertainties cannot be reduced by repeated measurements. The cause of systematic errors may be known or unknown. If both the cause and the value of a systematic error are known, it can be corrected for by "subtracting" the known deviation. However, there will still remain a systematic uncertainty component associated with this correction. Equipment • Engineering notebook • Gauge block Dial caliper
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