<prompt> Migration study is used to study:Sociodemographic reasons for migration of a populationPrevelence of disease in a populationEnvironment and genetic factors in a disease in populationDisease with Long incubation period  <response>: MIGRATION STUDIES Use: Evaluation of role of possible Genetic and Environmental factors in occurence of a disease in a population. Study Design: Comparision of Disease rates Death rates of, Migrants with kin who stayed at home. MIgrants with Local population of host country. Limitation: Non-random assignment to Groups: Migrants are self-selected Environmental factors may act at ceain agepoint only Not useful for disease with long incubation period Ref: Park 25th edition Pgno: 75 