A study found that the incidence of skin cancer increases along with the amount of time people work under fluorescent light, leading some people to conclude that fluorescent lighting is a cause of skin cancer. But further analysis found that people who work in offices, where fluorescent light is common, suffer more sunburn on their vacations than other workers. The sunburns, not the fluorescent light, were the cause of higher incidence of skin cancer. The original conclusion illustrates:
confusion of correlation and causation.