In a subsequent study to compare driving skills in subjects receiving and not receiving medication, adolescents with ADHD drove their own car on a standard road course after either taking OROS MPH at 8:00 AM or receiving no medication. (Cox 2004b) Raters, who were blinded to the medication condition, observed significantly fewer inattentive driving errors in adolescents taking OROS MPH (P<0.01). The study demonstrated that reduction in inattentive errors was positively correlated (r=0.60, P<0.01) with mg/kg dosing of OROS MPH.