Mdecine dobservation. Pierre-Charles Alexandre Louis (1787 1872) is often referred to as the father of clinical statistics.

Médecine d’observation. Pierre-Charles Alexandre Louis (1787–

1872) is often referred to as the “father of clinical statistics.” In 1837, he wrote “I conceive that without the aid of statistics nothing like real medical science is possible.”n In his most famous study, Louis evaluated bloodletting as a treatment for pneumonia. At the time, bloodletting was an extremely popular form of therapy. Two forms were practiced: by lancet (cutting a vein) and by placement of leeches on specific body parts.o Louis called into question the effectiveness of these therapies by carefully monitoring and recording outcomes in treatment groups. In one analysis, he compared patients who received early bloodletting (treatment group)
to those who received late treatment (control group). He found that 18 of 41 patients in the early treatment group died. In contrast, 9 of 36 control patients died.p

(a) Calculate the risk difference in the groups.

(b) Test the difference for significance. Report a two-tailed P-value for the test. Interpret the results.