analysisofvariance classification costcontrol costofoperation costsandcostanalysis diagnosisrelatedgroups economicaspects economics facilityregulationandcontrol forecasting hospital hospitalization hospitalpatients hospitals hospitalutilization insurance lengthofstay mathematicalmodels methods newjersey newyork newyork(state) prospectivepayment statisticalmethods trends unitedstates wx157a769n1984 wx157s634i