Derived numerical factors are those factors whose levels are calculated from the levels of other design factors. They can also be used to define linear constraints between factors, such that a value is only calculated when a categorical choice is made in another factor. Derived factors do not contribute to the calculation or power of the DOE design, as they are directly dependent on the factors that do contribute to the design.
A possible use case is if you want one of the liquids added to your mixtures to always be a specific ratio greater than the concentration of another liquid in your mixture. For example, it is common in mammalian cell transfection for the amount of transfection reagent used to be a certain ratio greater than the DNA concentration. As such, you might want to investigate the effect of different DNA concentrations, but also what the best ratio of transfection reagent to use is. To do this, you can define two design factors:
DNA concentration, between 1 and 3 ug/ml.
Ratio of transfection reagent to DNA, between 2 and 3.
From these two design factors you can derive what the actual transfection reagent concentration should be in each run, depending on what is selected for the DNA concentration and the Ratio factors. For example:
By doing this, Synthace is able to use the calculated concentration values for the transfection reagent to know how much volume to add to the mixtures to satisfy the ratio level chosen in your design, for any specific run.
To learn about the different types of functions supported for derived numerical factors click here.
To learn how to define derived numerical factors in Synthace click here.