2. How does variance analysis work?

2.1 Simple case: study of a single factor

From an Excel spreadsheet studying a single "operator" factor with three repetitions r 1, r 2 and r 3 (see figure Design of experiments studying one factor), we are able to identify qualified variations:

• intra-series, dispersion within a data series (represented by an oval);

• of interseries, dispersion of averages for each series (represented by a rectangle).

The sum of these dispersions is referred to as overall or total variation.