From fa12b10c6f94b93e28383e937119352749729b11 Mon Sep 17 00:00:00 2001
From: uhensler <urs.hensler@frentix.com>
Date: Wed, 18 Dec 2019 09:32:00 +0100
Subject: [PATCH] OO-4426: Calculate variance if exactly two users have
participated in a survey
---
.../manager/RubricStatisticCalculator.java | 2 +-
.../RubricStatisticCalculatorTest.java | 29 +++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/src/main/java/org/olat/modules/forms/manager/RubricStatisticCalculator.java b/src/main/java/org/olat/modules/forms/manager/RubricStatisticCalculator.java
index 18021e82c3e..57543d01ea6 100644
--- a/src/main/java/org/olat/modules/forms/manager/RubricStatisticCalculator.java
+++ b/src/main/java/org/olat/modules/forms/manager/RubricStatisticCalculator.java
@@ -203,7 +203,7 @@ class RubricStatisticCalculator {
size++;
}
}
- return size > 2? varianceDividend/(size - 1): null;
+ return size > 1? varianceDividend/(size - 1): null;
}
Double getStdDev(Double variance) {
diff --git a/src/test/java/org/olat/modules/forms/manager/RubricStatisticCalculatorTest.java b/src/test/java/org/olat/modules/forms/manager/RubricStatisticCalculatorTest.java
index 007d1181eef..fba4312069f 100644
--- a/src/test/java/org/olat/modules/forms/manager/RubricStatisticCalculatorTest.java
+++ b/src/test/java/org/olat/modules/forms/manager/RubricStatisticCalculatorTest.java
@@ -201,6 +201,35 @@ public class RubricStatisticCalculatorTest {
assertThat(variance).isEqualTo(1.5);
}
+ @Test
+ public void shouldCalculateSliderVarianceOfTwoResponses() {
+ ScaleType scaleType = ScaleType.oneToMax;
+ StepCountsBuilder stepCountsBuilder = StepCountsBuilder.builder(4);
+ stepCountsBuilder.withCount(1, Long.valueOf(1));
+ stepCountsBuilder.withCount(2, Long.valueOf(1));
+ stepCountsBuilder.withCount(3, Long.valueOf(0));
+ stepCountsBuilder.withCount(4, Long.valueOf(0));
+ SumMean sumMean = sut.getSumMean(stepCountsBuilder.build(), scaleType);
+
+ Double variance = sut.getVariance(stepCountsBuilder.build(), scaleType, sumMean.getMean());
+
+ assertThat(variance).isEqualTo(0.5);
+ }
+ @Test
+ public void shouldCalculateSliderVarianceOfOneResponse() {
+ ScaleType scaleType = ScaleType.oneToMax;
+ StepCountsBuilder stepCountsBuilder = StepCountsBuilder.builder(4);
+ stepCountsBuilder.withCount(1, Long.valueOf(1));
+ stepCountsBuilder.withCount(2, Long.valueOf(0));
+ stepCountsBuilder.withCount(3, Long.valueOf(0));
+ stepCountsBuilder.withCount(4, Long.valueOf(0));
+ SumMean sumMean = sut.getSumMean(stepCountsBuilder.build(), scaleType);
+
+ Double variance = sut.getVariance(stepCountsBuilder.build(), scaleType, sumMean.getMean());
+
+ assertThat(variance).isNull();
+ }
+
@Test
public void shouldCalculateSliderVarianceScaled() {
ScaleType scaleType = ScaleType.zeroBallanced;
--
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