Accuracy refers to how close a measured value is to the actual true value, while precision refers to how close repeated measurements are to each other. A measurement can be precise but not accurate if measurements are clustered but not near the true value, or accurate but not precise if measurements are scattered but the average is near the true value. Factors that affect accuracy include calibration standards, the workpiece being measured, measuring instruments, the person performing measurements, and environmental conditions.

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Prepared by,
Mr. S. B. Kamble
Department of Mechanical Engineering
Sharad Institute of Technology, College of Engineering, Yadrav
Accuracy and Precision
Subject – Metrology and Quality Control

2. Accuracy
Precision

4. Accuracy
Precision
Accuracy is how close a measured
value is to the actual (true) value.
Precision is how close the measured
values are to each other.

5. Dimension
Frequency
Dimension
Frequency
Dimension
Frequency
Distinction between Accuracy and Precision
Average
True Value
Average
Average
True Value
True Value
Precise but not Accurate Accurate but not Precise
Accurate and Precise
Error
Error

6. Accuracy and Cost
Cost
Accuracy
Max
Min
Min
Max
Calibration Standards
Workpiece being Measured
Measuring Instruments
Person or Inspector carrying
out the measurements
Environmental conditions
S
W
I
P
E

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