Computations based on uniform or normal distribution

The equation for estimating the standard deviation of the correction
assumes that biases are uniformly
distributed between {max bias, + max bias}. This assumption
is quite conservative. It gives a larger uncertainty than the
assumption that the biases are
normally distributed. If normality is a more reasonable
assumption, substitute the number '3' for the 'square root of 3'
in the equation above.
