The statement 'Majority of the people are average, a few very bright and few very dull' is based on which of the following principles?

The statement ' Majority of the people are average, a few very bright and few very dull' is based on the established principle of distribution of intelligence. As in the above statement level of  intelligence is distributed in average, bright and dull. As incase of any class room we can clearly observe that some of the students in class, score high who are bright students, some will score average and few will fail who are refered as dull students of the class.