  NASA's Kepler mission is providing basic asteroseismic data for hundreds of
stars. One of the more common ways of determining stellar characteristics from
these data is by so-called "grid based" modelling. We have made a detailed
study of grid-based analysis techniques to study the errors (and
error-correlations) involved. As had been reported earlier, we find that it is
relatively easy to get very precise values of stellar radii using grid-based
techniques. However, we find that there are small, but significant, biases that
can result because of the grid of models used. The biases can be minimized if
metallicity is known. Masses cannot be determined as precisely as the radii,
and suffer from larger systematic effects. We also find that the errors in mass
and radius are correlated. A positive consequence of this correlation is that
log g can be determined both precisely and accurately with almost no systematic
biases. Radii and log g can be determined with almost no model dependence to
within 5% for realistic estimates of error in asteroseismic and conventional
observations. Errors in mass can be somewhat higher unless accurate metallicity
estimates are available. Age estimates of individual stars are the most model
dependent. The errors are larger too. However, we find that for star-clusters,
it is possible to get a relatively precise age if one assumes that all stars in
a given cluster have the same age.
