Final answer:
Florence Nightingale used data visualization to show the impact of preventable infectious diseases in medical facilities during the Crimean War, leading to reforms in healthcare.
Step-by-step explanation:
Florence Nightingale used simple data visualization to change medical facility conditions by keeping meticulous records and analyzing the causes of illness and death during the Crimean War. In her analysis, she presented monthly frequency data on causes of death in a wedge chart histogram, which illustrated that the majority of casualties occurred due to preventable infectious diseases caused by poor sanitation and lack of access to hospital facilities. Nightingale's findings led to reforms in the British military's medical care.