Rim weighting calculates weights using a form of regression analysis. This requires a limit that defines how close the weighting procedure must get to the targets you define in order for the weights to be acceptable, and the number of times the weight calculations might be repeated in the attempt to reach the targets. Each time the weight calculations are performed is called an iteration.

At the end of each iteration, the Weight component compares the root mean square with the product of the weighted total and the given limit. The iterations continue until the root mean square is within the limit, in which case weighting is considered successful, or until the maximum number of iterations has been reached. If, after the maximum number of iterations, the root mean square is still outside the limit, the Weight component reports the failure in the weighting report (see Weighting report). However, the weights that have been calculated are still written to the case data variable.

The default limit is 0.005 and the default number of iterations is 12. However, you can change these parameters using the Weight.RimLimit and Weight.RimIterations properties. For example, you might want to reduce the limit and increase the number of iterations on a large sample to increase the accuracy of the weights.

You can also request that the weighting report gives details of the weights calculated at the end of each iteration instead of merely at the end of the final iteration. You do this by setting the Weight.RimReportInDetail property to True.

The weighting report highlights rim weights that are outside of a specified range. By default, the range is defined as 0.6-1.4. However, you can specify a different range using the Weight.RimFlagBelow and Weight.RimFlagAbove properties.