<prompt> All of the following are Experimental Interventional studies except:Randomised control trials .Field trials.Community trials.Ecological studies.  <response>: Ecological study Correlational study:Type of analytical observational epidemiological study which provide the least satisfactory type of evidence on causalityUnits of study: PopulationAdvantage: Data can be used from populations with different characteristicsPotential problem: Socio-economic confoundingEcological fallacy: Is an error of interpretation of statistical data in an ecological study, whereby characteristics are ascribed to a group of individuals which they may not possess as individuals 