[...] * For example, we can compare how in-scope units included in Big Data differ from in-scope units missing from the Big Data. To assess the difference, it is useful to consider the use of covariates, or variables that contain information that allows to determine the “profile” of the units (for example, geographic location, size, age, etc.) to create domains of interest. It is within these domains that comparisons should be made for “outcome” or study variables of interest (for example, energy consumption, hours worked, etc.). Note that the covariates chosen to create the domains should be related to the study variables being compared.