PPT Slide

Analysis of cluster RCTs.

Given:

492 patient RCT. Mortality was reduced from 36% (82/223) to 24% (67/269).

Dead Alive Total

control 82 67.5 141 223

treated 67 202 269

149 343 492

?2 = Sum [(Observed - Expected)2/ (Expected)]

Observed = 82

Expected = joint probability of being Control (223/492) AND of being Dead (149/492)

= (223/492)*(149/492) = 149*223/492

= 67.5

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