Study on the Normal and Skewed Distribution of Isometric Grouping

Because of thinking only the number of numbers but not fitting function, it would be adequate to take further afield when calculating group numbers with empirical formula. We have proved the three theorems based on studying the normal distribution, and then reach the conclusion that there is a better method to do the same work. The method is simpler and more practical than empirical method and also works well with any skewed distribution.