A two-stage test can be viewed as a family of decreasing functions f[c](p1) in the unit square. Each of these functions is a conditional error function, specifying the type I error conditional on the p-value p1 of the first stage. For example, f[c](p1) = min(1, c/p1) corresponds to Fisher's combination test. Based on this function family, the test can be put into practice by specifying the desired overall level alpha, stopping bounds alpha1 LE alpha0 and a parameter alpha2. After computing p1, the test stops with or without rejection of the null hypothesis if p1 LE alpha1 or p1 GT alpha0, respectively. Otherwise, the null hypothesis is rejected if and only if p2 LE f[c](p1), where c is such that the local level of this latter test is alpha2.
The four parameters alpha, alpha0, alpha1 and alpha2 are interdependent, and the form of their functional relationship depends on the test under consideration. For example, for Fisher's combination test, alpha = alpha1 + c(alpha2) * (ln(alpha0) - ln(alpha1)). This program provides functions that calculate any of the four parameters based on the remaining ones. Currently, this is done for the following four tests: Bauer/Koehne 1994, Lehmacher/Wassmer 1999, Vandemeulebroecke 2006, and the horizontal conditional error function.
The functions are part of the package adaptTest. The package and further informations about the package and the author can be found via CRAN.