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Accuracy vs. Precision.

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Presentation on theme: "Accuracy vs. Precision."— Presentation transcript:

1 Accuracy vs. Precision

2 Accuracy Accuracy = the extent to which a measured value agrees with a standard value Accuracy of a device must be checked Does it read a proper accepted value? Beware of Parallax – the apparent shift in position when viewed at a different angle.

3 Example: Accuracy Who is more accurate when measuring a book that has a true length of 17.0 cm? Susan: 17.0 cm, 16.0 cm, 18.0 cm, 15.0 cm Amy: 15.5 cm, 15.0 cm, 15.2 cm, 15.3 cm

4 Precision Precision = the degree of exactness of a measurement that is repeatedly recorded. Which set is more precise? 18.2 , 18.4 , 18.35 17.9 , 18.3 , 18.85 16.8 , 17.2 , 19.44

5 Example: Precision Who is more precise when measuring the same cm book? Susan: 17.0 cm, 16.0 cm, 18.0 cm, 15.0 cm Amy: 15.5 cm, 15.0 cm, 15.2 cm, 15.3 cm

6 Accuracy vs Precision Groupings Precise, not accurate
Accurate, not precise Precise and accurate Groupings

7 Accuracy vs. Precision Less Precise More Precise More Accurate
Less Accurate x

8 Accuracy vs Precision

9 Accuracy vs. Precision High Accuracy High Precision
High Precision Low Accuracy

10 Can you hit the bull's-eye?
Three targets with three arrows each to shoot. Both accurate and precise Precise but not accurate Neither accurate nor precise How do they compare? Can you define accuracy vs. precision?


12 Graduated Cylinder – Meniscus and Parallax

13 Why Is There Uncertainty?
Measurements are performed with instruments, and no instrument can read to an infinite number of decimal places Which of the instruments below has the greatest uncertainty in measurement?

14 Evaluate whether the following are precise, accurate or both.
High Accuracy High Precision Low Accuracy Low Precision Low Accuracy High Precision

15 Accuracy vs Precision


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