Examining bodies such as The Kenya National Examinations Council award certificates that are honored for meriting students for productive employment in the Kenyan economy. However it is not very clear how effective examining bodies are in awarding Certificates to diploma graduates with relevant skills and competencies required by the public sector of the economy. This study explored the effect of KNEC Diploma training on job performance. To do this, the research sought to establish the effects of duration taken in college, content of KNEC Diploma syllabus and field attachment for Diploma students on job performance. The study is significant since it was able to assess justification for further investment in the technical education and training systems as it currently exists in order to encourage economic development. The study was based on Job Market signaling model developed by Michael Spencer (1973). The model stipulates that the longer the duration taken in post-secondary education the more competent the candidate will be.