Table MTT0U. Two group t-test (unequal n’s)

Computed using t and non-central t distributions. The non-centrality parameter is δ(sqrt(n1))(sqrt(r))/sqrt(1+r) where δ is defined in the table row title and r = n2/n1 , the ratio of sample sizes. See nQuery Advisor® manual Appendix for details of computing method for t. Figure MTT0U shows computations for two examples. Additional values tested: parameter values same as for MTT0 with sample size ratios of 1, 2, 4 and 1/4. Checked against MTT0 for equal n’s and against DOS software Stat-Power version 2.0 by Bavry JL (1991) Scientific Software, Inc and SOLO Statistical System Power Analysis by Hintze JL (1991) BMDP Statistical Software.

Figure MTT0U. In the first and second columns, nQuery Advisor® 7.0 solved for sample size, in the third column for power and in the fourth column for effect size.