Which statement correctly defines repeatability and accuracy?

• A. Repeatability is the closeness to the true target; accuracy is the ability to return to the same pose.
• B. They are the same.
• C. Repeatability is the ability to return to the same pose consistently; accuracy is how close the pose is to the true target.
• D. Repeatability equals the average error; accuracy equals standard deviation.

Answer: (C)

The key idea here is understanding how repeatability and accuracy differ in robot positioning. Repeatability is about consistency: when you command the robot to move to the same pose multiple times, how tightly do the results cluster? It reflects the spread of repeated measurements—the smaller the spread, the higher the repeatability. Accuracy, on the other hand, is about closeness to the true target: it’s the bias between the average pose you achieve and the actual desired position or orientation.

So the best description is that repeatability is the ability to return to the same pose consistently, while accuracy is how close that pose is to the true target. If the robot lands in nearly the same place every time but that place isn’t the target, it’s highly repeatable but not very accurate. The other statements mix up these ideas, either swapping the definitions, claiming they’re the same, or conflating average error with dispersion.