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Accuracy and Repeatability Targets

Run the Accuracy and Repeatability Targets MicroSim Fullscreen

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Description

Classify four sets of five landing points on a target as accurate, repeatable, both or neither, then see the mean point and the spread that decide the answer. Used in Chapter 2.

Each set is five landing points, written as offsets in millimeters from the target and plotted as dots. Every plot uses the same scale, 5 mm each way from the target, so a tight group looks tight and a scattered group looks scattered. The orange ring marks 0.5 mm around the target.

The landing points are illustrative, and the 0.5 mm limit is a teaching value. Set 2 is the worked example from the chapter. After you answer, the sim marks the mean landing point with a red square and draws the smallest circle around the mean that holds all five points.

Lesson Plan

Grade level: Middle school and up (age 12+). Time: 5 to 10 minutes.

  1. Ask two questions. Is the group of dots centered on the target? Is the group tight? Use the table of offsets as well as the picture.
  2. Commit a label. Choose one of the four labels and press Check. You get one attempt per set.
  3. Read the measurements. The mean offset, its distance from the target and the largest distance from the mean are shown, with the reason for the label.
  4. Compare. The last screen shows all four sets side by side at the same scale. Mastery is 3 of 4.
  5. Think about it. Sets 2 and 4 are both about 2.2 mm off target. Which arm could be fixed with one calibration correction, and why?

Specification

The learning objective, evidence of mastery and content for this MicroSim are specified in Chapter 2: Anatomy of a Robot Arm.

References

  1. Accuracy and precision - Wikipedia - The difference between being close to the true value and being close to your own earlier results.