The Quality of a Measurement:Validity and Reliability
Someone learning archery must first learn how to hit the center of the target, and then to do it consistently. This is analogous to the validity and reliability of a measurement (103). The consistency (or reliability) of a measurement would be represented by how close successive arrows fall to each other, wherever they land on the target. Validity would be represented by the aim of the shooting—how close, on average, the shots come to the center of the target. Ideally, a close grouping of shots should lie at the center of the target (reliable and valid), but a close grouping of shots may strike away from the center, representing an archer who is consistently off target, or a test that is reliable but not valid, perhaps due to measurement bias.