Table 1 provides examples of the types of variables and responses for a chemical process. A continuous variable is a factor whose values can easily be adjusted over a range (quantitative factor). A categorical variable is a factor that is non-continuous (qualitative factor).
|Substrate A/B ratio||Substrate A/ Substrate B||Conversion|
|Rate of addition||Solvent||Rate or rate constant|
|pH||Order of addition||Purity / impurities|
|Time||Type of equipment||Isolated yield|
When selecting factors to study, use prior knowledge where available (previous observations, literature knowledge, related chemistry, etc.) and choose factors that are likely to answer the experimental objectives.