Tools for blinded sample size re-estimation (BSSR) in two-arm clinical
trials with binary endpoints, together with the exact power and sample size
calculations that the re-estimation relies on. Five exact statistical tests are
implemented: Pearson chi-squared, Fisher exact, Fisher mid-p, Z-pooled exact
unconditional, and Boschloo exact unconditional. Each test is available with a
one-sided or a two-sided alternative, and the exact unconditional tests can be
combined with the Berger-Boos procedure. Sample sizes can be re-estimated either at
the planning stage, to study the operating characteristics of a design, or from the
blinded data of a trial that is under way. Statistical methods based on Mehrotra et
al. (2003)