Exact calculations for sequential t, X² and F tests

Sequential and group sequential procedures are proposed for monitoring repeated t, X2 or F statistics. These can be used to construct sequential hypothesis tests or repeated confidence intervals when the parameter of interest is a normal mean with unknown variance or a multivariate normal mean with variance matrix known or known up to a scale factor. Exact methods for calculating error probabilities and sample size distributions are described and tables of critical values needed to implement the procedures are provided.