What can repeated readings reveal?

Repeated measurements show how much readings vary. A tight group can be very repeatable yet still miss a known reference. Compare both the spread and the group’s position relative to that reference. More readings do not automatically remove a consistent error. A measurement process is characterised by both variability and possible bias under specified conditions. Repetition supplies evidence about variation, whereas checking against an appropriate reference addresses a different question. The mean and range here are descriptive summaries of demonstration data. They do not fully characterise uncertainty or justify deleting inconvenient observations.