Suppose that you have a research study about risks factors for kidney disease in a specific area (in the area live few people). In recent years there was a high prevalence of this disease (unfortunately many deaths) and you have the supposition that environmental factors affect kidney disease. A survey with a sample size of 50 was taken but the information of the persons who died was not taken account in the research.
The conclusion of the study was that the environmental factors does not affect kidney disease. Why the environmental effect does not affect kidney disease? How can you explain this result to other people (non-statistician) who believe fervently that the data must reflect the relationship between kidney disease and environmental factors?