Table 1. CUSUM Equations and Variables Used to Construct a CUSUM Chart.

Variable	Value
p0 (Acceptable failure rate)	0.05
p1 (Unacceptable failure rate)	0.10
α (Probability type I error)	0.05
β (Probability type II error)	0.20
P = ln (p1 / p0)	0.69
Q = ln [(1 – p0) / (1 – p1)]	0.05
s = Q / (P + Q)	0.07
1 – S	0.93
a = ln [(1 – β) / α]	2.77
b = ln [(1 – α) / β]	1.56
h0 = −b / (P + Q)	−2.09
h1 = a / (P + Q)	3.71

CUSUM: cumulative sum.