diff --git a/src/main/java/org/olat/modules/quality/analysis/QualityAnalysisService.java b/src/main/java/org/olat/modules/quality/analysis/QualityAnalysisService.java
index 6e44ba293fe9c1c5f86d4fc8e8bcef1156c1feee..2a7b5b5b8ff43cc67bb0142a128e999eda790329 100644
--- a/src/main/java/org/olat/modules/quality/analysis/QualityAnalysisService.java
+++ b/src/main/java/org/olat/modules/quality/analysis/QualityAnalysisService.java
@@ -98,9 +98,6 @@ public interface QualityAnalysisService {
 	
 	public MultiTrendSeries<String> calculateIdentifierTrends(AnalysisSearchParameter searchParams,
 			Collection<String> responseIdentifiers, Collection<Rubric> rubrics, TemporalGroupBy temporalGroupBy);
-	
-	public MultiTrendSeries<MultiKey> calculateTrends(AnalysisSearchParameter searchParams,
-			Rubric rubric, MultiGroupBy groupBy, TemporalGroupBy temporalGroupBy);
 
 	/**
 	 * Calculate trend of multiple rubrics. Before using this method, make sure,
diff --git a/src/main/java/org/olat/modules/quality/analysis/manager/QualityAnalysisServiceImpl.java b/src/main/java/org/olat/modules/quality/analysis/manager/QualityAnalysisServiceImpl.java
index e4e65d90e26bede053669d68342519a0ebd4e262..6a8ccbe7d4ca0fe8c7815215fa0bb7a1b717974a 100644
--- a/src/main/java/org/olat/modules/quality/analysis/manager/QualityAnalysisServiceImpl.java
+++ b/src/main/java/org/olat/modules/quality/analysis/manager/QualityAnalysisServiceImpl.java
@@ -19,7 +19,6 @@
  */
 package org.olat.modules.quality.analysis.manager;
 
-import static java.util.Collections.singletonList;
 import static java.util.stream.Collectors.toList;
 
 import java.util.Collection;
@@ -316,19 +315,6 @@ public class QualityAnalysisServiceImpl implements QualityAnalysisService {
 		return statisticsCalculator.getTrendsByIdentifiers(statistics, temporalGroupBy);
 	}
 
-	@Override
-	public MultiTrendSeries<MultiKey> calculateTrends(AnalysisSearchParameter searchParams, Rubric rubric,
-			MultiGroupBy groupBy, TemporalGroupBy temporalGroupBy) {
-		if (groupBy == null || temporalGroupBy == null) return new MultiTrendSeries<>();
-		
-		List<String> identifiers = rubric.getSliders().stream().map(Slider::getId).collect(toList());
-		List<RawGroupedStatistic> statisticsList = filterDao.loadGroupedStatistic(searchParams,
-				identifiers, true, groupBy, temporalGroupBy);
-		GroupedStatistics<RawGroupedStatistic> rawStatistics = new GroupedStatistics<>(statisticsList);
-		GroupedStatistics<GroupedStatistic> statistics = statisticsCalculator.getGroupedStatistics(rawStatistics, singletonList(rubric));
-		return statisticsCalculator.getTrendsByMultiKey(statistics, temporalGroupBy);
-	}
-
 	@Override
 	public MultiTrendSeries<MultiKey> calculateTrends(AnalysisSearchParameter searchParams,
 			Set<Rubric> rubrics, MultiGroupBy groupBy, TemporalGroupBy temporalGroupBy) {
diff --git a/src/main/java/org/olat/modules/quality/analysis/manager/StatisticsCalculator.java b/src/main/java/org/olat/modules/quality/analysis/manager/StatisticsCalculator.java
index c3dba002073abbe6cc485cee842cba30f2078c14..4d3c43d3e8968722a462945bf5da4437baaff080 100644
--- a/src/main/java/org/olat/modules/quality/analysis/manager/StatisticsCalculator.java
+++ b/src/main/java/org/olat/modules/quality/analysis/manager/StatisticsCalculator.java
@@ -69,6 +69,10 @@ public class StatisticsCalculator {
 		GroupedStatistics<GroupedStatistic> statistics = new GroupedStatistics<>();
 		for (RawGroupedStatistic rawStatistic : rawStatistics.getStatistics()) {
 			Rubric rubric = identifierToRubric.get(rawStatistic.getIdentifier());
+			if (rubric == null) {
+				// fallback for trend (grouped by rubric / grouped by all)
+				rubric = getFirstRubric(rubrics);
+			}
 			if (rubric != null) {
 				GroupedStatistic statistic = getGroupedStatistic(rawStatistic, rubric);
 				statistics.putStatistic(statistic);
@@ -77,6 +81,13 @@ public class StatisticsCalculator {
 		return statistics;
 	}
 	
+	private Rubric getFirstRubric(Collection<Rubric> rubrics) {
+		for (Rubric rubric : rubrics) {
+			return rubric;
+		}
+		return null;
+	}
+	
 	private Map<String, Rubric> getIdentifierToRubric(Collection<Rubric> rubrics) {
 		Map<String, Rubric> identifierToRubric = new HashMap<>();
 		for (Rubric rubric : rubrics) {