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Measurement Reliability. Precision & Accuracy. Precision. The degree to which several measurements provide answers very close to each other. Indicator of the scatter in the data. The less the scatter, The higher the precision. . Accuracy.

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measurement reliability

Measurement Reliability

Precision & Accuracy

precision
Precision
  • The degree to which several measurements provide answers very close to each other.
  • Indicator of the scatter in the data.
    • The less the scatter, The higher the precision.
accuracy
Accuracy
  • The nearness of a measurement to the standard or actual value.
precision1
Precision
  • Assesses data with many measurements and no accepted (target) value
  • Quantified using uncertainty
    • Largest deviation from mean
    • Smaller deviations, better precision
accuracy1
Accuracy
  • Assess one measurement or many measurements
  • Quantified with % error
    • (experimental) – (accepted) X 100 (accepted)
accurate or precise
Accurate or Precise?
  • Baseball player hits the ball directly to the shortstop every time at bat.
  • Darts player hits the bulls eye with every shot.

Precise

Precise & Accurate

accurate or precise1
Accurate or Precise?
  • Soccer player hits the right goal post with every shot on goal.
  • Basketball player sometimes makes a basket, sometimes bounces off the rim, sometimes hits the back board, and sometimes shoots straight over the back board.

Precise

Not Precise Or Accurate

errors random errors
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.
errors systematic errors
Errors: Systematic Errors
  • Mistake which does not change during the experiment.
  • Affect accuracy, not precision.
uncertainty calculations
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.
uncertainty calculations1
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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