Accuracy

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Accuracy vs. Precision
I have a splitting headache
Completely missed the dartboard!!!
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The line falls between23.1 and 23.2
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Accuracy

• Refers how close a measurement is to the actual
  (true) value.
• Dartboard Analogy
• The bulls eye is the actual point where a
  person is aiming for.

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Accurate

• correct. A measurement is considered accurate
  if correctly reflects the size of the object
  being measured.
• How close are you to the actual/accepted value?
• Does the practice of using body parts as
  measurement tools produce accurate results?

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Precision

• Refers how close a a group of measurements are to
  one another. (reproducibility)

Person 1 2 3 4 5
Measurement (cm) 1.25 1.26 1.24 1.25 1.26
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Precise

• A precise measurement is repeatable and reliable.
  Getting the same measurement each time.
• Does the practice of using body parts as
  measurement tools produce precise measurements?
  (were all of your results the same?)

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Accurate or precise?
Accurate and Precise!
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Accurate or Precise?
Accurate
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Accurate or Precise?
Accurate
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• We can never get a perfect measurement, the best
  that we can do is get as close as possible within
  the limitations of our measuring instruments.

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How to Measure Properly
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23.1?
The measurement extends between 23.1 and 23.2
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Therefore, we can be sure the measurement is 23.1?
This is where estimation comes into play
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Uncertainty in Measurements

• Person
• 1
• 2
• 3
• 4
• 5

Measurement (cm) 1.25 1.26 1.24 1.25 1.26
1st two numbers (1.2_) are certain.
Last number is (1.2?) uncertain.
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Every measurement REQUIRES only 1 estimation!!!