Table 2.

Total number of Trusts identified as outliers for mortality according to varying definitions of outlier status

	Follow-up period (days)
	0–30	0–90	0–180	0–365
Outside 3 s.d.	12	20	23	25
HMU	4	8	8	10
LMU	8	12	15	15
Outside 2 s.d.	49	54	50	55
HMU	21	27	23	22
LMU	28	27	27	33

Outlier definition was varied by follow-up period and by number of standard deviations (s.d.) from mean mortality. HMU, high-mortality unit; LMU, low-mortality unit.