The SMRE evaluates the overall quality of data of each country data set included into the SMRE. For this purpose a special decision tree to make an intersubjective data evaluation was developed (see our working papers) and adopted to the growing amount of data and new data evaluation techniques of the SMRE.
The decision tree is used as a standardized country evaluation scheme. It assigns one of four possible categories of data quality to each case (i.e. a given country at each period reported). For each case the data quality is classified either as
- reliable (1),
- probably reliable (2),
- problematic (3) or
- not available (4).
The category assigned to the case is the result of the various steps taken by following the sequences of the decision tree.
In sum, the results of applying the decision tree and the various tests and procedures implemented in the SMRE on data quality lead statistically to a ‘conservative’ judgment on the quality of data. Thus, our data sets for cases classified as reliable can be taken as a highly precise approximation to the actual situation of religious affiliation in a respective European country for a given period in time.