Statistical Analysis

Proportion of Deaths: Clinic 1 vs Clinic 2 (1841–1846)

Mean before washing

0.105

Mean after washing

0.0211

Mean difference

-0.084

Handwashing reduced the proportion of deaths by approximately -0.084 (absolute).

Lower bound (2.5 %)

-0.1017

Upper bound (97.5 %)

-0.067

With 95 % confidence, handwashing reduced the monthly death proportion by between 10.17% and 6.7% (absolute reduction).

t-statistic

9.6101

p-value

1.45e-15

✅ The difference is statistically significant (p < 0.05). Handwashing provably reduced mortality.

Clinic 1 (medical students performing autopsies) had consistently higher death proportions than Clinic 2 (midwife students) from 1841–1846.
After Semmelweis mandated handwashing in June 1847, deaths fell by roughly -0.084 in absolute proportion.
Bootstrap 95 % CI: [-0.1017, -0.067] — equivalent to a 10.17–6.7 percentage-point reduction.
Welch's t-test: t = 9.6101, p = 1.45e-15. Result is statistically significant.