Florence Nightingale used data visualization to prove that poor sanitation killed more soldiers than battle wounds.

In 1854, Florence Nightingale arrived at the Scutari hospital during the Crimean War and found horrific conditions. She began meticulously collecting data on mortality rates, discovering that ten times more soldiers were dying from diseases like typhus, typhoid, and cholera than from battle injuries. To communicate this to the British Parliament and Queen Victoria, she developed the Polar Area Diagram, also known as the Rose Diagram.This innovative chart visualized monthly deaths across three categories: preventable infections, wounds, and other causes. The large blue wedges representing infection deaths were significantly larger than the red wedges for wounds, making the data impossible to ignore. Her statistical evidence showed that the mortality rate dropped from 42 percent to just 2 percent after basic sanitary reforms were implemented.Nightingale's work was supported by the 1855 Sanitary Commission, which discovered that the hospital was built over a sewer. By applying statistical analysis to healthcare, she became the first female member of the Royal Statistical Society in 1858. Her legacy remains central to epidemiology, as she proved that data visualization could drive public policy and save millions of lives through improved hygiene.