For statistical analysis the objects were classified in different categories (Fig. 4) according to their consumption and compared to a normal distribution, which was determined on the basis of the same mean and standard deviation. There is a visible approximation between both distributions. The hypothesis that the sample is based on a normally distributed population could be verified by means of a 2-test [8], which confirmed this basic assumption. As a result, an extrapolation with the "Students t-distribution" was possible and the mean thermal end energy consumption of all new school buildings in Luxembourg was estimated with a 95% confidence interval at
93 ± 9 kWh/(m2a).