Table STT2. Two group test of equal exponential survival (n large), exponential dropout

Power and sample size are computed based on equations from Lakatos, E. and Lan, K.K.G. 1992. A comparison of sample size methods for the logrank statistic. Statistics in Medicine, 11: 179-91. The required number of events, E, is computed from formula 9.2 in Collett, D. (1994) Modelling Survival Data in Medical Research, Chapman & Hall. Checked against examples published in Iwane, M, Palensky J, Plante K (1997) A User’s Review of Commercial Sample Size Software for Design of Biomedical Studies Using Survival Data. Controlled Clinical Trials, 18:65-83.

Figure STT00. Parameter conversion for Example 2 from Iwane et al (1997) using nQuery Advisor® 7.0.

Figure STT2. Example 2 from Iwane et al (1997) using nQuery Advisor® 7.0. The first column solves for n from power and the second solves for power from n.