Postulate 3. Assignable causes of variation may be found and eliminated.

Both pure and applied science have gradually pushed further and further the requirements for accuracy and precision. However, applied science, particularly in the mass production of interchangeable parts, is even more exacting than pure science in certain matters of accuracy and precision.

Postulate 2. Constant systems of chance causes do exist in nature.

Rule 1. Original data should be presented in a way that will preserve the evidence in the original data for all the predictions assumed to be useful.

Postulate 1. All chance systems of causes are not alike in the sense that they enable us to predict the future in terms of the past.