What is the difference between accuracy and precision in the context of medical device calibration?

Accuracy and precision are two distinct concepts in the context of medical device calibration, each describing different aspects of measurement quality. Accuracy refers to how close a measurement is to the true or accepted value. A device is considered accurate if its readings consistently reflect the actual quantity being measured. For instance, if a blood pressure monitor consistently displays a blood pressure reading that is very close to the patient's actual blood pressure as determined by a calibrated reference device, the blood pressure monitor is considered accurate. Precision, on the other hand, refers to the repeatability or consistency of a series of measurements. A device is considered precise if it produces very similar readings when measuring the same quantity multiple times, regardless of whether those readings are close to the true value. For example, if a scale consistently displays the same weight for an object each time it is weighed, even if that weight is slightly different from the object's actual weight, the scale is considered precise. A device can be precise but not accurate, meaning it gives consistent readings that are far from the true value. Conversely, a device can be accurate on average but not precise, meaning its readings fluctuate around the true value. Ideally, a medical device should be both accurate and precise to ensure reliable and trustworthy measurements. Calibration involves adjusting a device to improve its accuracy, often by comparing its readings to a known standard and making corrections as needed. Even with calibration, it is important to evaluate the device's precision to fully understand its measurement capabilities.