In reply to poonamnlwd:
Is it multiples of 3.8 you want to use? Then simply randomize the factor like this:
rand int mult;
Then you can do the following in the driver:
delay = req.mult*3.8;
Or you do prior to randomizing: multiply with 10 and after randomizaion you are dividing by 10.
But I believ you want to select values from a given list in random order. Right?