An assessment of the accuracy of the least squares procedures of several computer software packages

Longley's data set is used as a basis for the following projects: firstly, to assess the numerical accuracy of the least squares procedures of several computer software packages. secondly, to calculate farebrother's single limit condition number empirically. finally, to assess the numerical effect of repeated matrix inversions. it mainly appears that mean-centering of the variables can substantially improve the numerical accuracy and stability of the computed ols-estimates. key words:numerical accuracy, ols-procedure, longley's test problem, condition number.;