| Independent variables (%w/v) | Symbols | Coded values | ||
| −1 | 0 | +1 | ||
| Glucose | A | 1.5 | 2 | 2.5 |
| Tryptone | B | 1.1 | 1.6 | 2.1 |
| Yeast extract | C | 1.1 | 1.6 | 2.1 |