 Complete the following phrase:  Human error refers to something having been done that was not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits. Human error has been cited as a primary cause contributing factor in disasters and accidents in industries as diverse as nuclear power e.g., the Three Mile Island accident, aviation see pilot error, space exploration e.g., the Space Shuttle Challenger disaster and 