Table 1.

Nominal human error rates of selected activities (adapted from Park²¹)

Activity*	Probability of human error (No of errors/No of opportunities for the error)
General error of commission—for example, misreading a label	0.003
General error of omission in the absence of reminders	0.01
General error of omission when items are embedded in a procedure—for example, cash card is returned from cash machine before money is dispensed	0.003
Simple arithmetic errors with self checking but without repeating the calculation on another sheet of paper	0.03
Monitor or inspector fails to recognise an error	0.1
Staff on different shifts fail to check hardware condition unless required by checklist or written directive	0.1
General error rate given very high stress levels where dangerous activities are occurring rapidly	0.25

^*Unless otherwise indicated, assumes the activities are performed under no undue time pressures or stress.