If the test rejects, then random effects is biased and fixed effects is the correct estimation procedure.

The Huber loss function describes the penalty incurred by an estimation procedure.

There should be ways of testing the performance of interval estimation procedures.

For a given estimation procedure in a given situation, the higher the confidence level, the wider the confidence interval will be.

Actually, we used above only one type of current carriers during estimation procedure.

Heckman (1976) proposed a two-stage estimation procedure using the inverse Mills ratio to take account of the selection bias.

Phylogenetic analysis: models and estimation procedures.

Paulson et al. (1975) and Heathcote (1977) provide some theoretical background for such an estimation procedure.

Generally these extensions make the estimation procedure more complex and time-consuming, and may also require more data in order to get an accurate model.

Thus least squares estimation is not necessarily an admissible estimation procedure.