Which test level can NOT be improved using the TMMi model?

The TMMi framework is applicable to all levels of testing, including static testing (such as reviews) and dynamic testing, regardless of the phase of the software development lifecycle. TMMi encompasses structured testing activities across various test levels such as component testing, integration testing, system testing, and user acceptance testing, along with both static and dynamic techniques. Therefore, all levels of testing can be improved using the TMMi model.