Lower stopping boundaries
=========================

For a multi-stage group-sequential design, **multiarm** requires a
choice about the type of lower (futility) stopping boundary to use. This
can be either fixed (a common interim value), O’Brien Fleming, Pocock,
or triangular. Specify your chosen type of lower stopping boundary here.
If fixed is chosen, an input box will appear for you to specify the
common fixed interim stopping boundary.
