Nightingale’s mission, from her “call to service,” was to save lives, which she initially understood as being through nursing the sick. From the Crimean War on, statistics were a means to that end of saving lives. Her 853-page, anonymous, analysis of 1858 shows this. She and Dr William Farr—it was always joint work-- developed a fine way to portray the data and make their points persuasively, with polar area charts.
Nightingale was also an astute user of simple bar charts. See her tribute to Sidney Herbert on his death, depicting how death rates declined under his leadership. My own bar chart comparing British and French death rates will show how much better the British did in learning the lessons of high death rates.
Nightingale’s two most famous books,
Notes on Nursing, 1860, and
Notes on Hospitals, 1863, set out the knowledge she gained from the statistical analysis, the positive application of the negatives learned from the war.