Certified Diagnosis Technician

Goodmorning,
my name is Serena and I'd like to make some questions about the Certified Diagnosis Technician (CDT).
Is the Certified Diagnosis Technician the person in charge of garage?
Is he responsible of his work colleagues?
Is he the head of garage?
Thank you for your answers. For me is more important know these answers.
 
I'm sorry for my expressions because I'm Italian.
 
Thanks
Serena.