Investigating the effect of intra-operative infiltration with local anaesthesia on the development of chronic postoperative pain after inguinal hernia repair. A randomized placebo controlled triple blinded and group sequential study design [NCT00484731]

Table 2 Threshold z-values for the χ²-test at each interim analysis

Interim analyses	Number of patients	Reject H₀ if z ≥	Accept H₀ if z <	Reject H₀ if p ≤
1	120	-2.9626	2.9626	0.0031
2	180	-2.359	2.359	0.0183
3 = final analysis	240	-2.0141	2.0141	0.044

ISSN: 1471-2482