How many of the digits in a mean of 12.3456789012 are worth reporting?

A computer program tells me that a mean value is 12.3456789012, but how many of these digits are significant (the rest being random junk)? Should I report: 12.3?, 12.3456?, or even 10 (if only the first digit ...

Source: BMC Research Notes - March 18, 2019 Category: Research Authors: R. S. Clymo Tags: Research note Source Type: research