Nowadays,how to understand and apply the concept of faith is a hot issue in the academic circle.

Analysis method of GUM is all-purpose and effective, when confidence level is small, analysis method of ITTC will be limited and analysis method of GUM will be recommended for use.

Computer auto-arithmetic for confidence probability and interval with normal distribution;

Investigations on principle of Monte Carlo simulation was made when considering characteri-(stics) of AWGN(additive white Gaussian noise) channel and the affects of three suitable parameters: error number,confidence probability and max relative error of simulation result.

Both the analysis and the description are proved to be well within high confidence probability and claim many advantages as a necessity for college physics experimentation teaching.

A new computational formula of fiducial probability in consideration of sample size and subsample standard deviation is derived from the least squares principle.

With the assumption that random error obeys normal distribution,and that system error is subject to uniform distribution,the distribution of the two kinds of combination misalignment obey was calculated according to probability knowledge,and then fiducial probability of the corresponding confidence interval was determined.