initializeSegmentRecord is an internal function
for creating a new segment record.
initializeSegmentRecord(simulation_constants)initializeSegmentRecord returns a list containing segment record.
freq_true is a length-n_segment vector containing the number of times examinees belonged in each theta segment, based on true thetas.
freq_est is a length-n_segment vector containing the number of times examinees belonged in each theta segment, based on final theta estimates.
count_true
count_est
a named list containing simulation constants.