Farr’s contribution is the tradition of using vital statistical data to study health problems. His studies compared married to single persons, workers in different occupations (metal mines and earthenware industry), elevations above sea level, and the effects of incarceration.

If your class did not complete Module 1a, you might want to include at this point the slides from that module on John Snow and cholera in London, which provide a dramatic illustration of epidemiologic analysis.