© 1987 by Biometrika Trust
Asymmetry of estimators in nonlinear regression
CSIRO Division of Mathematics and Statistics Canberra, ACT2601, Australia
The least-squares estimators of nonlinear regression parameters are partitioned into three terms. Only the first is symmetrically distributed. Measures of asymmetry are derived from the other two which are valid for any sample size in that, if they are both zero for a given parameter, then its estimator is exactly symmetrically distributed. Asymptotic results are derived and we find that all odd central moments have a common factor when evaluated to first order. This factor relates to the second term only, as does the bias. To first order, the second term consists of parameter effects, in that it may be removed by transformation, whereas the third term is intrinsic.
Key Words: Asymmetric distribution Least-squares estimator Measure of asymmetry Nonlinear regression