Table 6.

 Tests for carryover effect by comparison of the clusters of cardiopulmonary resuscitations (CPR) outside hospital first randomised to feedback-on with those clusters first randomised to feedback-off during the first two randomisation periods of trial*

Outcome	Difference of feedback-on from feedback-off
	Average percentage change in cluster outcome rates (95% CI)		P value for test of carryover
	Feedback-on first clusters	Feedback-off first clusters
Prehospital return of spontaneous circulation	−8.4 (−17.4 to 0.7)	−7.3 (−17.5 to 2.9)	0.865
Survival to hospital discharge	−5.6 (−11.9 to 0.8)	−5.3 (−11.7 to 1.0)	0.959

*Trial of CPR provided by emergency medical services with monitor-defibrillator providing real-time feedback on CPR process (“feedback-on”) or not providing feedback (“feedback-off”).