When implementing RTI, there are at least three phases to progress monitoring where data is collected and analyzed:
Baseline Phase - where data is collected prior to the initiation of an intervention. Assessments made at this level are often used as a "pre-testing" data agains which a later comparion is made to determine whether progress was significant
Intervention Phase - where the designed intervention has been implemented. The length of this phase, namely, how long the intervention will last, is determined by the RTI Team using the on-going data collected
Response to Intervention Phase - where student progress is monitored over a pre-determined amount of time, after teh interventions have been fully implemented
Source: National Professional Resources, Inc.