Accuracy vs Precision

Processes and their measurement systems can suffer from low accuracy, low precision or both. Measurement accuracy concerns closeness to a true or accepted reference; precision concerns agreement among repeated measurements under stated conditions. Both support sound business decisions. Meeting a process target or specification is a separate requirement.

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Accuracy vs Precision

At the top left, the darts cluster away from the target center: high precision but low accuracy. The center represents the true or accepted reference value. Reduce the systematic offset while retaining the small spread to move toward the lower illustration, where measurements are close to the reference and to each other.

At the top right, the schematic darts stay near the reference but are more dispersed: the high-accuracy/low-precision example. Their center is near the target, but individual results vary. A centered average alone does not establish accurate individual measurements. Reduce the spread while maintaining centering to reach the lower illustration, with high accuracy and high precision. These darts are schematic examples, not measured observations.