I'm confused about the meaning and usage of response time and turnaround time. As far as I know, response time is the time between the arrival of a task until the first response (first step to execute the task) and the turnaround time is the time between arrival of a task to the completion of the task execution, but I found this formula for average response time in several research paper  and :
ART = 1/N ∑ (Finish_Time - Arrival_Time)
Arrival_Time is when a task arrives and Finish_time is when the task leaves the system.
Does this formula represent Average response time or average turnaround time?