Chapter 1 Measurements

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Chapter 1Measurements

• Accuracy and Precision

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Accuracy

• How close a measurement is to the actual or true
  value
• good accuracy
• true value
• poor accuracy
• true value

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Precision

• How well several measurements agree with each
  other
• good precision
• poor precision

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Accuracy and Precision

• What can you say about the accuracy and
  precision in each of the following
• Good precision, poor accuracy
• Good precision, good accuracy

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• In your new job, you are to make the pizzas the
  size shown above. Your first four pizzas are
  shown below.
• What can you say about the accuracy and
  precision of your pizzas?

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The next four pizzas.

• What can you say about the accuracy and
  precision of the next four pizzas?

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Accuracy is improving.

• The two pizzas in the center show good accuracy.
  However, the precision is poor.

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Pizza Precision

• You have very good precision, but poor accuracy.
  I think the customers will want the pizzas made
  larger.

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Learning Check AP1

• Match the following terms
• 1) Accuracy 2) Precision
• ___ How close a measurement is to the
• true value.
• ___ How close several measurements
• are to each other.
• Can you have data that are precise, but not
  accurate? Why or why not?

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Solution AP1

• Match the following terms
• 1) Accuracy 2) Precision
• _1_ Is how close a measurement is to the
• true value.
• _2_ Is how close several measurements
• are to each other.
• Yes. Data can be precise, but not come close
  to the true value.

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Learning Check AP2

• How will each of the following affect accuracy
  and precision?
• 1. A meter stick that is missing the first
  centimeter.
• 2. A scale that has a zero point that is really
  five pounds above zero.

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Solution AP2

• How will each of the following affect accuracy
  and precision?
• 1. The shortened meter stick will produce
  measurements that have poor accuracy, but good
  precision is possible.
• 2. The poorly calibrated scale will give a
  weight that is not accurate, but good precision
  is possible.

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Learning Check AP3

• True(1) or false (2). Measurements can have
• poor accuracy and poor precision
• good accuracy and poor precision
• poor accuracy and good precision
• good accuracy and good precision

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Learning Check AP3

• True(1) or false (2). Measurements can have
• poor accuracy and poor precision
• good accuracy and poor precision
• poor accuracy and good precision
• good accuracy and good precision

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