Applying cusum-based methods for the detection of outbreaks of Ross River virus disease in Western Australia

Table 2 Algorithm summary performance statistics for false alarm rates approximating 0.001^†

Algorithm	false alarm rate	median (mean) sensitivity	Day 1 sensitivity	Day 2 sensitivity	Days 1–7 sensitivity	CARL	median (mean) timeliness^‡	median (mean) adjusted timeliness^‡
EARS C1	0.0008	0 (0.27)	0.13	0	0.13	1.0	36.5 (49.0)	123 (113.1)
EARS C2	0.0008	0 (0.40)	0.13	0	0.13	1.0	44.5 (52.7)	90 (96.0)
EARS C3	0.0008	0 (0.47)	0.13	0	0.13	1.0	51.0 (52.4)	73 (93.4)
NBC 7-day	0.0008	1 (0.80)	0.13	0.07	0.27	1.8	19.5 (32.3)	21 (31.1)
NBC 14-day	0.0008	1 (0.80)	0.07	0	0.13	2.0	33.5 (39.0)	32 (36.5)
NBC 28-day	0.0008	1 (0.93)	0.07	0	0.2	3.0	16.5 (26.3)	18 (26.8)
NBC 56-day	0.0008	1 (0.80)	0	0	0.13	5.0	19.0 (31.0)	20 (30.1)
p-value^¥	-	<0.0001	-	-	-	-	0.91	0.0003

^†Test threshold that produced a false alarm rate ≤ 0.001
^‡Detection on the first outbreak day is equivalent to a timeliness of 0 days
^¥Friedman rank sum test
CARL: Conditional Average Run Length – conditional on the detection of the outbreak during the first 7 days
EARS: Early Aberration Reporting System
NBC: Negative binomial cusum with an out of control state defined as 2 standard deviations greater than the mean

ISSN: 1472-6947