## How to make good use of the qualitatives …

EstimLab makes use of many data to establish a relation between cost – or something else (as the duration, or the number of hours, or anything else ) – and variables you have selected (or have asked EstimLab to select).

These variables can be many as the software accepts up to 30 quantitative variables (to which one can associate a number) and 16 « qualitative » variables, each one having several « modalities ».

These quantitative variables are very important in cost estimating and can rarely be substituted.

Because of their nature, one can’t associate a number to those variables. Each one has “modalities”. For example for a supplier, the modalities will be the name of each supplier; another qualitative variable could be the product’s material, in which case the modalities could be a list such as steel, aluminium, titanium etc …

*How are these variables used in conjunction with the quantitative variables * (such as mass, power or flow). Two possible solutions

- the first one consists in considering that the relation between the cost and the quantitative variables remains the same for each modality in the set of the qualitative variables. The influence of these qualitative variables just shifts, more or less, the relation between the cost and the quantitative variables. This is the easiest solution.

- the second implies that each modality (for the given set of qualitative variables) can disturb the relation. One then searches for as many relations as existing modalities.

Now how can one decide between these two alternatives ?

EstimLab has a procedure that gives you the parts of the answer with just one click.