To present the situation of air quality in European Cities, in an understandable manner, all detailed measurements are processed in a single digit relative: CAQI
. Three different indices were developed to allow comparison of three different time scales:
The comprehensive pretesting program for POLS would not have been possible without CAQI as a pretesting technique perfectly adapted to the computerized data collection design.
For the use of CAQI in the qualitative operational test of Step 3, a distinction should be made between meta-questions for the respondent, and evaluation questions for the interviewer (about the mixed-mode procedure, general impressions, etc.).