Examples of Variables and Responses for a Chemical Process

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).

Table 1
Variables		Responses
Continuous	Categorical	Responses
Substrate A/B ratio	Substrate A/ Substrate B	Conversion
Reagent quality		Regioselectivity
Temperature		Stereoselectivity
Concentration	Reagent	Enatioselectivity
Rate of addition	Solvent	Rate or rate constant
pH	Order of addition	Purity / impurities
Time	Type of equipment	Isolated yield
Pressure		Particle size
Agitation rate		Density

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.