Technique for Human Error Rate Prediction

The THERP approach is based on the results of a task analysis, which breaks a task into a number of subtasks. Then makes this subtask array into an assembly of discrete HRA subtasks, forming an HRA event tree. To quantify this HRA event tree, one should select the appropriate human error probabilities to match the subtasks in the HRA event tree.
THERP is a task-defined HRA type mode. The elements considered are developed by carrying out a task analysis on the specific HRA task to be modeled and quantified. Within the set of subtasks to consider are series tasks, parallel tasks, and recoveries.
Reference: Human reliability assessment: theory and practice
Technical Tools/Human Factors and Errors/Human Reliability Analysis/Task Related