...a/org/olat/modules/quality/analysis/GroupedStatistic.java

...a/org/olat/modules/quality/analysis/HeatMapStatistic.java

...olat/modules/quality/analysis/QualityAnalysisService.java

.../quality/analysis/manager/QualityAnalysisServiceImpl.java

...odules/quality/analysis/manager/StatisticsCalculator.java

.../modules/quality/analysis/model/HeatMapStatisticImpl.java

...t/modules/quality/analysis/ui/FooterGroupByDataModel.java

...g/olat/modules/quality/analysis/ui/GroupByController.java

...rg/olat/modules/quality/analysis/ui/GroupByDataModel.java

...g/olat/modules/quality/analysis/ui/HeatMapController.java

...org/olat/modules/quality/analysis/ui/HeatMapRenderer.java

...org/olat/modules/quality/analysis/ui/TrendController.java

...ules/quality/analysis/ui/_i18n/LocalStrings_de.properties

...ules/quality/analysis/ui/_i18n/LocalStrings_en.properties

...es/quality/analysis/manager/StatisticsCalculatorTest.java