With factor weighting, every record which satisfies a given set of conditions is assigned a specific weight. You would generally use it when the weights are calculated outside of Quantum; for example, you might be told that all unemployed people in London require a weight of 10.5, whereas unemployed people in the rest of the country need a weight of 7.3.

When Quantum creates the weighted table, it will check which cell of the weighting matrix each respondent belongs in, and will apply the weight associated with that cell before placing the respondent in the table.

You can also use factor weighting, with a factor of 1.0, when you just want to use weights stored in the data or calculated in the edit, without defining any other weights. These weights are defined as preweights. For an example, see Using weights in the record alone.