Qm
Statistics

New hygiene protocol in one ward: diff-in-diff

difference-in-differencescausal-inferencehealthcare

A hospital introduces a new hygiene protocol in Ward A and keeps Ward B, similar in patient mix, as a control. Infection rates before and after:

  • Ward A (treated): 12% before, 6% after.
  • Ward B (control): 12% before, 10% after.

Compute the difference-in-differences estimate of the protocol's effect, and interpret the sign given that lower is better.

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