
Confidence
Measures
381
the side of being too large. This helps to smooth out the effects of
sampling error. Even more importantly, it tends to broaden the
rejection tail, resulting in more conservative confidence measures.
Examination of the above graphs shows that blurring is very signifi-
cant at σ = 0.1, so this should probably be an upper limit.
More definitive statements can be made, though. If
we
include
σ in the definition of the Gaussian window function:
-(-)
2
20-8
W(d) = e °
we can rewrite this formula to tell us the difference in activation levels
needed to reduce the influence of a sample point to a given fraction of
the maximum