hi aabid,
for practical perpective there is always some randomness in components,thus there behaviour or response will vary from time to time.
this random may some times enhance or degrade the system performance by some amount.
the randomness is probabilistic, and if we take more no of sweeps the no. of sweeps that cause in degradation will eual the sweeps that ehhance system performace.thus taking mean of all the sweeps will provide us better practical readings
we can disable randomness,for simulation purposes, but it has practical importance as stated above.
with regards