Accuracy and Precision

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Accuracy and Precision

• Measurements are qualitative or quantitative.
• Qualitative measurements give results that are
  descriptive and non-numerical.
• Example
• Quantitative measurements give results that are
  definite, usually as numbers and units.
• Example

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a)78.1 mL, 43.9 mL, 2 mL accurate precise
both neither b) 68.1 mL, 68.2 mL, 68.0
mL accurate precise both neither c) 98.0
mL, 98.2 mL, 97.9 mL accurate precise both
neither d) 72.0 mL, 60.3 mL, 68.1 mL
accurate precise both neither
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Accuracy and Precision

• Measurements work best when they are accurate and
  precise
• Accuracy is a measure of how close a measurement
  comes to the actual or true value of whatever is
  measured.
• To evaluate the accuracy of a measurement, it
  must be compared to the correct value.
• Precision is a measure of how close a series of
  measurements are to one another.
• The precision of a measurement depends on more
  than one measurement.

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Accuracy and Precision
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Accuracy and Precision
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Accuracy and Precision

• In this picture, all of the darts land on the
  bulls-eye which illustrates good precision and
  accuracy.
• In this picture, all of the darts land near each
  other, but away from the bulls-eye which
  illustrates good precision, but poor accuracy.

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Accuracy and Precision

• Here the darts are not close to each other, but
  are close to the bulls-eye indicating poor
  precision, but good accuracy.
• Finally, the darts are not close to each other or
  near the bulls-eye indicating both poor accuracy
  and poor precision.

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Accuracy and Precision

• What is the following an example of
• You did an experiment to see at what degree water
  boiled in Celsius.
• You got the following results.
• T1- 65
• T2- 67
• T3 66
• Accuracy or Precision????

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Accuracy and Precision

• A basketball player throws 100 free-throws 95
  of these balls go through the goal 5 miss the
  goal entirely. Describe the precision and
  accuracy of the free-throws.

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The same player is having an off day 5 balls go
through the goal the other 95 balls bounce off
of the rim. Describe the precision and accuracy
of the throws .
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Each of five students used the same ruler to
measure the length of the same pencil. These
data resulted 15.33 cm, 15.34 cm, 15.33 cm,
15.33 cm, 15.34 cm. The actual length of the
pencil was 15.85 cm. Describe whether accuracy
and precision are each good or poor for these
measurements.
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Draw a target diagram that shows precision but
not accuracy .
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Draw a target diagram that shows accuracy but not
precision
14
Draw a target diagram that shows both accuracy
and precision