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1.27: Accuracy and Precision

Difficulty Level: At Grade Created by: CK-12
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Have you ever played golf, like the person in this photo? Even if you haven’t played golf before, you probably know that the goal of the game is to hit the ball into a hole with the fewest strokes of the club. Golf is a good way to understand two important concepts in scientific measurement: accuracy and precision.

Accuracy

The accuracy of a measurement is how close the measurement is to the true value. If you were to hit four different golf balls toward an over-sized hole, all of them might land in the hole. These shots would all be accurate because they all landed in the hole. This is illustrated in the sketch below.

Precision

As you can see from the sketch above, the four golf balls did not land as close to one another as they could have. Each one landed in a different part of the hole. Therefore, these shots are not very precise. The precision of measurements is how close they are to each other. If you make the same measurement twice, the answers are precise if they are the same or at least very close to one another. The golf balls in the sketch below landed quite close together in a cluster, so they would be considered precise. However, they are all far from the hole, so they are not accurate.

Golf balls demonstrating precision

Q: If you were to hit four golf balls toward a hole and your shots were both accurate and precise, where would the balls land?

A: All four golf balls would land in the hole (accurate) and also very close to one another (precise).

Summary

  • Accuracy means making measurements that are close to the true value.
  • Precision means making measurements that are close in value to each other but not necessarily close to the true value.

Review

  1. Complete this statement: A measurement is accurate when it is __________.
  2. What makes two measurements precise?
  3. Kami measured the volume of a liquid three times and got these results: 66.71 mL, 66.70 mL, 66.69 mL. The actual volume of the liquid is 69.70 mL. Are Kami’s measurements precise? Are they accurate? Explain your answers.

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Vocabulary

accuracy

Closeness of a measurement to the true value.

precision

Exactness of a measurement.

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Difficulty Level:
At Grade
Grades:
7 , 8
Date Created:
Oct 31, 2012
Last Modified:
Sep 13, 2016
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