This report examines the linkage between the quality of enlisted personnel (in terms of aptitude score) and their ability to operate the Patriot air defense missile system. The intent was to help the Army set appropriate performance standards and estimate the effects of personnel quality on operational performance. The study finds that the Armed Forces Qualification Test (AFQT) score has a direct, consistent effect on the outcomes of air battles, both in terms of knowledge assessed by written tests and in actual performance simulations. Specifically, soldiers with higher AFQT scores can be expected to suffer significantly less asset damage, destroy more hostile aircraft, and be more effective in missile conservation. The study also finds that a one-level change in AFQT category equaled or surpassed the effect of a year of operator experience or of frequent training, a finding that has significant readiness and cost implications, since higher quality soldiers require less training and operator experience. Finally, the study finds that next to AFQT, operator and unit experience are the factors that most consistently affect performance.