Under Operational Test and Evaluation (OT&E), testing must verify the level of operational effectiveness and suitability a system has to meet the user’s needs. The evaluation is conducted at the Full Rate Production Decision Review (FRPDR). During Initial Operational Test and Evaluation (IOT&E), an estimate of the operational effectiveness and suitability of the system is developed.
Evaluation of Operational Effectiveness 
Operational effectiveness is the overall degree of mission accomplishment of a system when used by representative personnel in the environment planned or expected for operational employment of the system considering organization, training, doctrine, tactics, survivability, vulnerability, and threat.
The evaluation of operational effectiveness is linked to mission accomplishment. The early planning for the evaluation should consider any special test requirements, such as the need for large test areas or ranges or supporting forces, requirements for threat systems or simulators, new instrumentation, or other unique support requirements.
For weapon systems, integrate Live-Fire Test and Evaluation (LFT&E) of system lethality into the evaluation of weapon system effectiveness. For example, operational testing could identify likely shot lines, hit points, burst points, or miss distances that might provide a context for LFT&E lethality assessments. Fuse performance, as determined under Developmental Test and Evaluation (DT&E), could provide information for both OT&E and LFT&E assessments.
Evaluation of Operational Suitability 
Operational suitability is the degree to which a system can be satisfactorily placed in field use, with consideration given to reliability, availability, compatibility, transportability, interoperability, wartime usage rates, maintainability, safety, human factors, manpower supportability, logistics supportability, documentation, environmental effects, and training requirements.
Early planning for the suitability evaluation should include any special needs for number of operating hours, environmental testing, maintenance demonstrations, testing profiles, usability of Developmental Test data, or other unique test requirements.
Operational suitability should be evaluated in a mission context in order to provide meaningful results. For example, maintaining a required operations tempo over an extended period while conducting realistic missions gives insight into the interactions of various suitability factors.
AcqLinks and References:
-  Defense Acquisition Guidebook (DAG) – Chapter 9
- DAU Test and Evaluation Management Guide, Jan 2005