setupData extracts treated/untreated subsets, ECDFs,
and auxiliary vectors from a QTEparams object and injects them
into the caller's environment via assign(..., envir=parent.frame()).
This side-effectful pattern is intentional — all compute.* functions
rely on the variables created here being available in their local scope.
setupData(qteParams)Invisibly returns NULL. The function's effect is the
assignment of data objects into the calling environment.
A QTEparams object holding the function parameters.