A disease whose etiology is not known, the first step in the formation of hypothesis will be-

in descriptive epidemilogy,it is regarded as the first phase of epidemiological investigations.the basic procedures in a descriptive study includes, 1.defining the poppulation at risk. 2.defining the disease under study. 3.describing the disease by time,place and person. 4.measurement of the disease. 5.comparing with known indices. 6.formulation of an aetiological hypothesis. ref:park&;s textbook,ed 22,pg no 60