Precision and validity

(A) Dartboard illustrating high precision but low validity. The darts can be interpreted as representing studies attempting to measure the true effect (the bullseye). The studies closely approximate an estimate, but it is not the "true" effect.
(B) Dartboard illustrating low precision but high validity. As in the previous example, the darts can be interpreted as representing studies attempting to measure the "true" effect (the bullseye). In this case, the studies closely approximate the "true" effect (the bullseye), but the studies vary in their individual estimates. Interpretation of group of studies like this give a less confident assessment that they have revealed the "truth" compared with the group of studies that gave highly precise estimates (arrows tightly clustered within the bullseye).