Ans - Decrease and Increase Both.
Example for decrease in the average turn round time :
Suppose we have two process P1 and P2 with burst time 20 sec and 2 sec respectively. P1 arrives at time t= 0 sec and P2 at t=2 sec.
When time quantum for RR = 1 sec.
Then TAT for P1 = 22 sec. and for P2 = 3 sec.
So AVG TAT = (22 + 3 ) /2 sec.
Now do same with time quantum for RR = 2 sec.
You will get AVG TAT = (22 + 2 )/2 sec.
Example for increase in the average turn round time :
Suppose we have two process P1 and P2 with burst time 20 sec and 5 sec respectively. P1 arrives at time t= 0 sec and P2 at t=5 sec.
When time quantum for RR = 5 sec.
Then TAT for P1 = 25 sec. and for P2 = 5 sec.
So AVG TAT = (25 + 5 ) /2 sec.
Now do same with time quantum for RR = 6 sec.
You will get AVG TAT = (25 + 6 )/2 sec.