3. The decision after observation

To decide is to foresee. To foresee is to calculate.

To calculate, the engineer has at his disposal the tools of statistical laws studied in the article Random Processes. . We remind you that these laws are defined as mathematical beings, independent of any observation. They do, however, admit a central tendency defined in an abstract way (the mathematical expectation E [X ]) and a dispersion characterized, also, in an abstract way (the standard deviationσ ).

Armed with this theoretical background, the engineer will imagine – it's his responsibility, not that of the course – that the central tendency on the one hand, and the dispersion on the other, present a certain stability with regard to the phenomenon studied and the measurements made. He will consider that one of the laws in the statistical arsenal describes the measurements...