Walter A. Shewhart Quotes

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

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.

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.

Every sentence in order to have definite scientific meaning must be practically or at least theoretically verifiable as either true or false upon the basis of experimental measurements either practically or theoretically obtainable by carrying out a definite and previously specified operation in the future. The meaning of such a sentence is the method of its verification.

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