Advanced Physics for Brachytherapy 2018

Type A uncertainty

➢ Recall that :

b, the stdev of unknown quantity m is not known but for N>>

approximates m

and the square root of the variance

approximates b.

therefore forms precision confidence interval (k=3) of our tally and it must be

as low as possible.

➢ Type A uncertainty decreases ~ 1/sqrt(N)

➢ type A uncertainty decreases as voxel size increases for analogue MC (at the expense of volume averaging)

➢ the only other way to decrease type A would be to reduce Var(k) which is in essence an efficiency gain and will be discussed later