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Measurement Reliability

Measurement Reliability. Precision & Accuracy. Precision & Accuracy. pre·ci·sion ( pr-szhn ) - n . The ability of a measurement to be consistently reproduced. ac·cu·ra·cy ( kyr -- s) - n . The ability of a measurement to match the actual value of the quantity being measured.

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Measurement Reliability

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  1. Measurement Reliability

  2. Precision & Accuracy

  3. Precision & Accuracy pre·ci·sion (pr-szhn) - n. • The ability of a measurement to be consistently reproduced. ac·cu·ra·cy (kyr--s) - n. • The ability of a measurement to match the actual value of the quantity being measured.

  4. Precision & Accuracy • Precision • Assesses data with many measurements and no accepted (target) value • Quantified using uncertainty • Largest deviation from mean • Mean +/- uncertainty => range of the result • Accuracy • Assess one measurement or many measurements • Quantified with % error • (experimental) – (accepted) X 100 (accepted)

  5. Uncertainty Calculations • Calculate mean • Calculate difference between each measurement and the mean (the deviation) • Use the largest of these values as the uncertainty • The smaller the range, the more precise.

  6. Errors Random errors • Unnoticed variations in technique, tiny changes in the experimental environment, etc. • Affect precision. • Truly random effects average out over a large number of trials. Systematic errors • Mistake which does not change during the experiment. • Affect accuracy, not precision.

  7. Uncertainty Calculations • Calculate mean • Calculate difference between each measurement and the mean (the deviation) • Use the largest of these values as the uncertainty • Value in range of 0.741 to 0.765 • The smaller the range, the more precise.

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