Edward R. Tufte
...lace data in an appropriate context for assessing cause and effect (Tufte, 1990, p. 141). Tufte describes how the original data listed the victim’s names and described their circumstances, all in order by date of death. Tufte further explains that the time-series display (chronologies of the epidemic) is not causal explanation but instead a poor variable and useless in discovering a strategy to halt the epidemic (142). Tufte continues by explaining how Snow did not simply report a days bad news, but instead constructed a graphical display that provided direct and powerful testimony about a cause-effect relationship. Snow derived a spatial comparison from the original one-dimensional data, including a map marking the deaths from cholera along with the location of community water pumps. Tufte points out that Snow’s map shows an intense cluster of deaths near the Broad Street pump, as compared to other local water sources with a lack of deaths, concluding a strong association between cholera and the proximity of the notorious Broad Street well (142). 2. Make quantative comparisons (Tufte, 1990, p. 142). Tufte states that the fundamental question in statistical analysis is “compared with what?”. Therefore, investigating the victims of cholera is insufficient as credible evidence; to understand the cause of the epidemic requires an analysis of those who escaped the disease. Tufte mentions that with great clarity Dr. Snow did compare the living and the dead by reporting a nearby brewery and a similarly close workhouse. Although the brewery was near the Broad Street well, the seventy unaffected workmen drank beer instead of water, and if they did drink water, there was a well inside the brewery. Also a nearby workhouse with over five hundred thirty five inmates survived with only five casualties because of a pump-well on the premises. (144) Interesting enough, the five deaths that did occur were admitted to the workhouse after being infected. 3. Consider alternative explanations and contrary cases (Tufte, 1990, p.144). Tufte expands with “the point is to get it right, not to win the case, not to sweep under the rug all the assorted puzzles and inconsistencies that frequently occur in collections of data” (144). He also commends Dr. Snow on not hiding the fact that a few deaths appear unrelated to the Broad Street pump. As it turns out, “Dr. Fraser” called to Snow’s attention that actually the few victims that lived away from the contaminated well sent a cart to get a bottle of Broad Street water daily, because of the preferred taste. Tufte also commends Snow on being saintly, unlike some researchers, and gives full credit to Dr. Fraser for finding this crucial evidence. (145) Tufte then becomes somewhat confusing by writing that Snow’s evidence is uncertain because it isn’t clear that the removal of the Broad Street pump-handle had much to do with ending the epidemic due to cholera already rapidly declining by that time. Tufte previously wrote that everyone abandoned their belongings and deserted the town, so of course cholera would be declining, who was left to contract the disease? Next Tufte talks about how at a minimum, removal of the pump-handle prevented a recurrence. Tufte seems to contradict the whole essay by implying that Dr. Snow merely saved lives by discoveri...