The phrase "as the main variable" is correct and usable in written English.
It can be used when discussing a primary factor or element in a particular context, such as research, analysis, or modeling.
Example: "In this study, we will focus on temperature as the main variable affecting plant growth."
Alternatives: "as the primary factor" or "as the key variable".
The dissolved oxygen concentration was identified as the main variable influencing the nitrite accumulation during nitrification.
IOP measurements, as the main variable, were obtained with Goldmann applanation tonometer (GAT; Haag-Streit, Konig, Switzerland) by the ophthalmologist masked to the randomization.
Of these, academic studies tend to stress the role of crowd support in swaying refereeing decisions as the main variable.
Moreover, this extremely fast convergence comes with the solution gradients (viscous stresses/heat fluxes for the Navier Stokes equations) simultaneously computed with the same order of accuracy as the main variable.
Software development companies today are widely using software functional size measurement (FSM) as the main variable to assess the effort and time needed to perform a new software project.
We show that numerical schemes constructed in this way can be automatically uniformly accurate, allow O(h) time step, and compute the solution gradients (viscous stresses/heat fluxes for the Navier Stokes equations) simultaneously to the same order of accuracy as the main variable, for all Reynolds numbers.
Architecture of reinforced layers and the content of fiber volume fraction used through the thickness were considered as the main variables of the proposed slabs.
Train speed and the type, span length and stiffness of the bridge were considered as the main variables in the analysis.
The experiments included die corner radius, punch die clearance, punch nose radius, pad force and material type as the main variables.
The crust nature, its degree of interaction with the stone and other factors related to the principle of the cleaning procedures were found as the main variables influencing the effectiveness of the cleaning procedures.
A first set of experiments allowed identifying the temperature, the time of contact and the ethanol proportion in the extraction solution, as the main variables affecting the extraction efficiency.
