The practical example of "error distribution" quoted in the article expounds the cause of"normal distribution", introduces the"standard score system" and sets forth another practical application of"normal distribution".

The class teaching quality of 31 teachers, who teach different classes, and courses, was evaluated by using educational statistics theory (standard fraction theory).

An evaluation system composed of eight evaluation indicators has been determinated in light of the specific conditions of the scientific research management in teacherscolleges,and a simple,rational and operational method for the assessment of scientific research is set up by adopting a standard fraction.

? Using the standard mark in education statistic method to explain exam grades can make certain each exam mark s position in the whole,and can carry on different subjects exam marks compare and combination,thus can avoid the limitation of original mark.

The applied method of standard marks is explained,and a practical handling method of standard marks is posed for the examination courses that the full mark is 150.

A test of goodness of fit on normality of sample distribution is given with Kolmogrof Smirnoff method, and a condition of standard score transformation is discussed.

The standard score is influenced by subjective factors only while free of the influence of such objective factors as the degree of difficulty and the degree of differentiation.