Trials-to-Criterion is a measurement that reflects the number of response opportunities or attempts needed for an individual to reach a specified level of accuracy or mastery of a skill. It indicates how many trials are required before the person can consistently perform the behavior at the desired level.
Example
A teacher is teaching a student how to tie their shoes. The teacher tracks the number of times the student practices (trials) before they can successfully tie their shoes without assistance on five consecutive attempts. If it takes 15 attempts to meet this criterion, the trials-to-criterion is 15.