A random sample of 10% (273) Norwegian general practitioners (GP) received a questionnaire including 11 case stories. For each case the GP was asked to fill in an action value for hemoglobin which should represent the minimal change considered necessary by that general practitioner to take action towards the patient. These minimal changes could then be used for calculation of imprecision goals assuming that there was no change in the bias of the two measurements. The analytical imprecision goals (CV) derived from the different case stories varied between 0% and 7.8% with a mean of 2.8% accepting a false positive rate of 5%. The GPs assessment of a single case story also varied substantially.