Helper function to Transform PVs onto a new metric (e.g., PISA Mean = 500, SD = 100). Uses the method described in the PISA 2012 technical manual.
transformPvs(data, mT = 0, sdT = 1, weights = 1)
a List of transformed PVs with as many elements as PVs were listed in 'x'.
A data frame or matrix that contains the PVs
The desired mean of the PVs
The desired sd of the PVs
a vector of weights, the same length as data[1]
used to
calculate the mean and SD across the PVs