  How important is an independent diameter measurement for the determination of
stellar parameters of solar-type stars? When coupled with seismic observables,
how well can we determine the stellar mass? If we can determine the radius of
the star to between 1% and 4%, how does this affect the theoretical
uncertainties? Interferometry can provide an independent radius determination
and it has been suggested that we should expect at least a 4% precision on such
a measurement for nearby solar-type stars. This study aims to provide both
qualitative and quantitive answers to these questions for a star such as our
Sun, where seismic information will be available. We show that the importance
of an independent radius measurement depends on the combination of observables
available and the size of the measurement errors. It is important for
determining all stellar parameters and in particular the mass, where a good
radius measurement can even allow us to determine the mass with a precision
better than 2%. Our results also show that measuring the small frequency
separation significantly improves the determination of the evolutionary stage
and the mixing-length parameter.
