(Florence) Nightingale's passion for statistics enabled her to persuade the government of the importance of a whole series of health reforms. for example, many people had argued that training nurses was a waste of time, because patients cared for by trained nurses actually had a higher mortality rate than those treated by untrained staff. Nightingale, however, pointed out that this was only because more serious cases were being sent to those wards with trained nurses. If the intention is to compare the results from two groups, then it is essential to assign patients randomly to the two groups. Sure enough, when Nightingale set up trials in which patients were randomly assigned to trained and untrained nurses, it became clear that the cohort of patients treated by trained nurses fared much better than their counterparts in wards with untrained nurses.