Skip to main content

Table 1 CUSUM equations and variables

From: The learning curve for minimally invasive Oxford phase 3 unicompartmental knee arthroplasty: cumulative summation test for learning curve (LC-CUSUM)

Variable

Value

p 0—acceptable UKA failure rate

0.20

p 1—unacceptable UKA failure rate

0.40

α—probability of the type I error

0.05

β—probability of the type II error

0.20

P = ln (p 1/p 0)

0.69

Q = ln [(1 − p 0)/(1 − p 1)]

0.29

s = Q/(P + Q)

0.29

1 − S

0.71

a = ln [(1 − β) / α]

2.77

b = ln [(1 − α) / β]

1.56

h 0 = − b / (P + Q)

−1.59

h 1 = a / (P + Q)

2.83