Surveys to answer questions. Some methodological considerations.
D002648:Child; D003625:Data Collection / Q000379:methods / Q000592:standards; D004739:England; D006306:Health Surveys; D006801:Humans; D008131:London; D001523:Mental Disorders / Q000175:diagnosis / Q000453:epidemiology*; D011594:Psychometrics; D012424:Rural Population; D012494:Sampling Studies; D014505:Urban Population