Table MTT0. Two group t-test (equal n’s)

Computed using t and non-central t distributions; the non-centrality parameter is δ(sqrt(n)) where δ is defined in the table row title. See nQuery Advisor® manual Appendix for details of computing method for t. Figure MTT0 shows computations for one example. Additional values tested: significance level .001, .20 one and two-sided by power of 50% and 99% and effect size of .05 and 6 to n, values of n equal to 6 and 2000 and effect sizes of .05 and 6 back to power. Checked against tables in Machin D, Campbell MJ (1987) Statistical Tables for the Design of Clinical Trials, Blackwell Scientific Publications Oxford, and DOS software Stat-Power version 2.0 by Bavry JL (1991) Scientific Software, Inc and Statistical System Power Analysis by Hintze JL (1991) BMDP Statistical Software.

Figure MTT0. In the first and fourth columns, nQuery Advisor® 7.0 has computed n, in the second column power, and in the third column, effect size.