Unit B: Measurement

Difference between Precision and Accuracy

The accuracy of a measurement is how close a result comes to the true value. The precision of a set of measurements tells you how closely the different values are to each other.

Compare the following bull's eyes in Figures 1 and 2. The darts thrown to the target are indicated by "x's" in the diagram.
 
  1. Which diagram shows that the darts are thrown more accurately?
  2. Which diagram shows that the darts are thrown more precisely?

    Figure 1


    Figure 2




 
  1. The darts shot in Figure 1 show a higher degree of accuracy since the darts are close to the bull's eye.
  2. The darts shot in Figure 2 demonstrate higher precision since the darts are grouped closer to each other.
Compare the following bull's eyes in Figures 3 and 4.

  1. Which diagram shows the darts are thrown more accurately?
  2. Which diagram shows the darts thrown less precisely?

Figure 3


Figure 4





  1. Figures 3 and 4 show equal accuracy since all four shots are contained within the bull's eye.
  2. Figure 3 demonstrates lower precision since the shots are more spread out when compared to the shots in Figure 4.
Compare the following bull's eyes in Figures 5 and 6.

Which diagram shows the darts thrown more accurately?
Which diagram shows the darts thrown more precisely?

Figure 5


Figure 6




 
  1. The darts shot in Figure 6 show higher accuracy since the darts are located in the bull's eye.
  2. Figures 5 and 6 show equal precision since both sets of shots are grouped closely together.
View the Accuracy and Precision video to reinforce these concepts.
Note: A paper towel roll is used to guide the placement of paper clips onto a target.