a chemical factory manufactures chemicals that could induce respiratory problems such as asthma or even lung cancer in people not properly protected from the fumes. if a factory employee at that chemical manufacturing plant develops any health problems (asthma, cancer, etc) they often quit, or are fired, or moved to an office job. if an epidemiological study was performed with the factory workers as participants, the results would likely be biased because the employees would be healthier than expected and lead to the wrong conclusion that working in the factory is safe. what type of bias is this an example of?