Index: Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/FailureMechanismSectionResult.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/FailureMechanismSectionResult.cs	(.../FailureMechanismSectionResult.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/FailureMechanismSectionResult.cs	(.../FailureMechanismSectionResult.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -21,11 +21,9 @@
 
 using System;
 using System.Collections.Generic;
-using System.Globalization;
 using System.Linq;
 using Core.Common.Base;
 using Core.Common.Base.Data;
-using CoreCommonResources = Core.Common.Base.Properties.Resources;
 
 namespace Ringtoets.Common.Data.FailureMechanism
 {
@@ -70,11 +68,22 @@
         /// <summary>
         /// Gets and sets the value of assessment layer two a.
         /// </summary>
-        public string AssessmentLayerTwoA
+        public RoundedDouble? AssessmentLayerTwoA
         {
             get
             {
-                return GetAssessmentResult();
+                var totalProbablity = (RoundedDouble?) 0.0;
+                foreach (var scenario in CalculationScenarios.Where(cs => cs.IsRelevant))
+                {
+                    if (!scenario.Probability.HasValue)
+                    {
+                        return null;
+                    }
+
+                    totalProbablity += (scenario.Contribution*scenario.Probability.Value);
+                }
+
+                return totalProbablity;
             }
         }
 
@@ -88,26 +97,17 @@
         /// </summary>
         public RoundedDouble AssessmentLayerThree { get; set; }
 
-        /// <summary>
-        /// Gets and sets a list of <see cref="ICalculationScenario"/>
-        /// </summary>
-        public List<ICalculationScenario> CalculationScenarios { get; private set; }
-
-        private string GetAssessmentResult()
+        public RoundedDouble TotalContribution
         {
-            var relevantScenarios = CalculationScenarios.Where(cs => cs.IsRelevant).ToList();
-            double totalContribution = relevantScenarios.Aggregate<ICalculationScenario, double>(0, (current, calculationScenario) => current + calculationScenario.Contribution);
-
-            if (relevantScenarios.Any() && Math.Abs(totalContribution - 1.0) > 1e-6)
+            get
             {
-                return double.NaN.ToString(CultureInfo.InvariantCulture);
+                return (RoundedDouble) CalculationScenarios.Where(cs => cs.IsRelevant).Aggregate<ICalculationScenario, double>(0, (current, calculationScenario) => current + calculationScenario.Contribution);
             }
-
-            var probability = relevantScenarios.Select(relevantScenario => relevantScenario.Contribution*relevantScenario.Probability).Aggregate(0.0, (current, probabilityContribution) => current + probabilityContribution);
-
-            return double.IsNaN(probability) || Math.Abs(probability) < 1e-6
-                       ? "-"
-                       : string.Format(CoreCommonResources.ProbabilityPerYearFormat, probability);
         }
+
+        /// <summary>
+        /// Gets and sets a list of <see cref="ICalculationScenario"/>
+        /// </summary>
+        public List<ICalculationScenario> CalculationScenarios { get; private set; }
     }
 }
\ No newline at end of file
Index: Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/ICalculationScenario.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/ICalculationScenario.cs	(.../ICalculationScenario.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/FailureMechanism/ICalculationScenario.cs	(.../ICalculationScenario.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -41,6 +41,6 @@
         /// <summary>
         /// Gets the probability of the scenario.
         /// </summary>
-        RoundedDouble Probability { get; }
+        RoundedDouble? Probability { get; }
     }
 }
\ No newline at end of file
Index: Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.Designer.cs
===================================================================
diff -u -r58c0d0a9d882210f47175f62ef1e4c494fce140b -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 58c0d0a9d882210f47175f62ef1e4c494fce140b)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -239,6 +239,26 @@
         }
         
         /// <summary>
+        ///   Looks up a localized string similar to Niet alle berekeningen voor dit vak zijn uitgevoerd..
+        /// </summary>
+        public static string FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_are_executed {
+            get {
+                return ResourceManager.GetString("FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_are_ex" +
+                        "ecuted", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to Niet alle berekeningen voor dit vak hebben een geldige uitkomst..
+        /// </summary>
+        public static string FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_have_valid_output {
+            get {
+                return ResourceManager.GetString("FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_have_v" +
+                        "alid_output", resourceCulture);
+            }
+        }
+        
+        /// <summary>
         ///   Looks up a localized string similar to Bijdrage van de geselecteerde scenario&apos;s voor dit vak zijn opgeteld niet gelijk aan 100%.
         /// </summary>
         public static string FailureMechanismResultView_DataGridViewCellFormatting_Scenario_contribution_for_this_section_not_100 {
@@ -304,6 +324,15 @@
         }
         
         /// <summary>
+        ///   Looks up a localized string similar to -.
+        /// </summary>
+        public static string FailureMechanismSectionResultRow_AssessmentLayerTwoA_No_result_dash {
+            get {
+                return ResourceManager.GetString("FailureMechanismSectionResultRow_AssessmentLayerTwoA_No_result_dash", resourceCulture);
+            }
+        }
+        
+        /// <summary>
         ///   Looks up a localized string similar to eindpunten.
         /// </summary>
         public static string FailureMechanismSections_EndPoints_DisplayName {
Index: Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.resx
===================================================================
diff -u -r58c0d0a9d882210f47175f62ef1e4c494fce140b -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.resx	(.../Resources.resx)	(revision 58c0d0a9d882210f47175f62ef1e4c494fce140b)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/Properties/Resources.resx	(.../Resources.resx)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -244,4 +244,13 @@
   <data name="FailureMechanismResultView_DataGridViewCellFormatting_Scenario_contribution_for_this_section_not_100" xml:space="preserve">
     <value>Bijdrage van de geselecteerde scenario's voor dit vak zijn opgeteld niet gelijk aan 100%</value>
   </data>
+  <data name="FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_are_executed" xml:space="preserve">
+    <value>Niet alle berekeningen voor dit vak zijn uitgevoerd.</value>
+  </data>
+  <data name="FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_have_valid_output" xml:space="preserve">
+    <value>Niet alle berekeningen voor dit vak hebben een geldige uitkomst.</value>
+  </data>
+  <data name="FailureMechanismSectionResultRow_AssessmentLayerTwoA_No_result_dash" xml:space="preserve">
+    <value>-</value>
+  </data>
 </root>
\ No newline at end of file
Index: Ringtoets/Common/src/Ringtoets.Common.Forms/Views/FailureMechanismResultView.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/src/Ringtoets.Common.Forms/Views/FailureMechanismResultView.cs	(.../FailureMechanismResultView.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Common/src/Ringtoets.Common.Forms/Views/FailureMechanismResultView.cs	(.../FailureMechanismResultView.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -22,13 +22,15 @@
 using System;
 using System.Collections.Generic;
 using System.Drawing;
+using System.Globalization;
 using System.Linq;
 using System.Windows.Forms;
 using Core.Common.Base;
 using Core.Common.Base.Data;
 using Core.Common.Controls.Views;
 using Ringtoets.Common.Data.FailureMechanism;
 using Ringtoets.Common.Forms.Properties;
+using CoreCommonResources = Core.Common.Base.Properties.Resources;
 
 namespace Ringtoets.Common.Forms.Views
 {
@@ -45,6 +47,7 @@
         private DataGridViewTextBoxColumn assessmentLayerTwoA;
         private DataGridViewTextBoxColumn assessmentLayerTwoB;
         private DataGridViewTextBoxColumn assessmentLayerThree;
+        private const double tolerance = 1e-6;
 
         /// <summary>
         /// Creates a new instance of <see cref="FailureMechanismResultView"/>.
@@ -229,7 +232,7 @@
 
         private class FailureMechanismSectionResultRow
         {
-            private readonly FailureMechanismSectionResult failureMechanismSectionResult;
+            public readonly FailureMechanismSectionResult failureMechanismSectionResult;
 
             public FailureMechanismSectionResultRow(FailureMechanismSectionResult failureMechanismSectionResult)
             {
@@ -261,7 +264,19 @@
             {
                 get
                 {
-                    return failureMechanismSectionResult.AssessmentLayerTwoA;
+                    if (failureMechanismSectionResult.CalculationScenarios.Any() && Math.Abs(failureMechanismSectionResult.TotalContribution - 1.0) > tolerance)
+                    {
+                        return double.NaN.ToString(CultureInfo.InvariantCulture);
+                    }
+
+                    var layerTwoA = failureMechanismSectionResult.AssessmentLayerTwoA;
+
+                    if (!failureMechanismSectionResult.CalculationScenarios.Any() || !layerTwoA.HasValue || double.IsNaN(layerTwoA.Value))
+                    {
+                        return Resources.FailureMechanismSectionResultRow_AssessmentLayerTwoA_No_result_dash;
+                    }
+
+                    return string.Format(CoreCommonResources.ProbabilityPerYearFormat, layerTwoA.Value);
                 }
             }
 
@@ -328,18 +343,44 @@
 
         private void DataGridViewCellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
         {
-            double doubleValue = 0;
-            if (e.Value != null)
-            {
-                double.TryParse(e.Value.ToString(), out doubleValue);
-            }
+            FailureMechanismSectionResultRow resultRow = dataGridView.Rows[e.RowIndex].DataBoundItem as FailureMechanismSectionResultRow;
 
-            if (e.ColumnIndex == assessmentLayerTwoA.Index)
+            if (resultRow != null && e.ColumnIndex == assessmentLayerTwoA.Index)
             {
-                dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = double.IsNaN(doubleValue)
-                                                                                   ? Resources.FailureMechanismResultView_DataGridViewCellFormatting_Scenario_contribution_for_this_section_not_100
-                                                                                   : string.Empty;
+                FailureMechanismSectionResult rowObject = resultRow.failureMechanismSectionResult;
+
+                if (rowObject.AssessmentLayerOne)
+                {
+                    dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = string.Empty;
+                    return;
+                }
+
+                if (rowObject.CalculationScenarios.Any() && Math.Abs(rowObject.TotalContribution - 1.0) > tolerance)
+                {
+                    dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = Resources.FailureMechanismResultView_DataGridViewCellFormatting_Scenario_contribution_for_this_section_not_100;
+                    return;
+                }
+
+                var layerTwoA = rowObject.AssessmentLayerTwoA;
+
+                if (!layerTwoA.HasValue)
+                {
+                    // Calculation not done.
+                    dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = Resources.FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_are_executed;
+                    return;
+                }
+                
+                if (double.IsNaN(layerTwoA.Value))
+                {
+                    // Calculation output not valid.
+                    dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = Resources.FailureMechanismResultView_DataGridViewCellFormatting_Not_all_calculations_have_valid_output;
+                    return;
+                }
+
+                dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = string.Empty;
             }
+
+            
         }
 
         #endregion
Index: Ringtoets/Common/test/Ringtoets.Common.Data.Test/FailureMechanism/FailureMechanismSectionResultTest.cs
===================================================================
diff -u -r8093a22c96deede9e51a3afa570de9a7cb2202a1 -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/test/Ringtoets.Common.Data.Test/FailureMechanism/FailureMechanismSectionResultTest.cs	(.../FailureMechanismSectionResultTest.cs)	(revision 8093a22c96deede9e51a3afa570de9a7cb2202a1)
+++ Ringtoets/Common/test/Ringtoets.Common.Data.Test/FailureMechanism/FailureMechanismSectionResultTest.cs	(.../FailureMechanismSectionResultTest.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -43,7 +43,7 @@
             // Assert
             Assert.AreSame(section, sectionResult.Section);
             Assert.IsFalse(sectionResult.AssessmentLayerOne);
-            Assert.AreEqual("-", sectionResult.AssessmentLayerTwoA);
+            Assert.AreEqual((RoundedDouble)0, sectionResult.AssessmentLayerTwoA);
             Assert.AreEqual((RoundedDouble)0, sectionResult.AssessmentLayerTwoB);
             Assert.AreEqual((RoundedDouble)0, sectionResult.AssessmentLayerThree);
             CollectionAssert.IsEmpty(sectionResult.CalculationScenarios);
@@ -61,32 +61,49 @@
         }
 
         [Test]
-        public void AssessmentLayerTwoA_ScenariosDoNotAddUpToHunderdPercent_ReturnsNaN()
+        [TestCase(true)]
+        [TestCase(false)]
+        public void AssessmentLayerOne_Always_ReturnsSetValue(bool newValue)
         {
             // Setup
             var section = CreateSection();
             var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
 
+            // Call
+            failureMechanismSectionResult.AssessmentLayerOne = newValue;
+
+            // Assert
+            Assert.AreEqual(newValue, failureMechanismSectionResult.AssessmentLayerOne);
+        }
+
+        [Test]
+        public void AssessmentLayerTwoA_ScenariosCalculated_ReturnsValue()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+
             var mocks = new MockRepository();
             var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
             calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
-            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)0.5);
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0);
+            var expectedProbability = (RoundedDouble)41661830;
+            calculationScenarioMock.Expect(cs => cs.Probability).Return(expectedProbability).Repeat.Twice();
 
             mocks.ReplayAll();
 
             failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock);
 
             // Call
-            double assessmentLayerTwoA;
-            double.TryParse(failureMechanismSectionResult.AssessmentLayerTwoA, out assessmentLayerTwoA);
+            var assessmentLayerTwoA = failureMechanismSectionResult.AssessmentLayerTwoA;
 
             // Assert
-            Assert.IsNaN(assessmentLayerTwoA);
+            Assert.AreEqual(expectedProbability, assessmentLayerTwoA);
             mocks.VerifyAll();
         }
 
         [Test]
-        public void AssessmentLayerTwoA_ScenariosAddUpToHunderdPercent_ReturnsValueAsString()
+        public void AssessmentLayerTwoA_ScenarioNotCalculated_ReturnsNull()
         {
             // Setup
             var section = CreateSection();
@@ -95,8 +112,7 @@
             var mocks = new MockRepository();
             var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
             calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
-            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Twice();
-            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble)41661830);
+            calculationScenarioMock.Expect(cs => cs.Probability).Return(null);
 
             mocks.ReplayAll();
 
@@ -106,12 +122,12 @@
             var assessmentLayerTwoA = failureMechanismSectionResult.AssessmentLayerTwoA;
 
             // Assert
-            Assert.AreEqual(string.Format("1/{0:N0}", 41661830), assessmentLayerTwoA);
+            Assert.IsNull(assessmentLayerTwoA);
             mocks.VerifyAll();
         }
 
         [Test]
-        public void AssessmentLayerTwoA_ScenariosAddUpToHunderdPercentScenarioNotCalculated_ReturnsString()
+        public void AssessmentLayerTwoA_ScenarioInvalidOutput_ReturnsNaN()
         {
             // Setup
             var section = CreateSection();
@@ -120,8 +136,8 @@
             var mocks = new MockRepository();
             var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
             calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
-            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Twice();
-            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble)double.NaN);
+            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble?) double.NaN).Repeat.Twice();
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble) 1.0);
 
             mocks.ReplayAll();
 
@@ -131,10 +147,116 @@
             var assessmentLayerTwoA = failureMechanismSectionResult.AssessmentLayerTwoA;
 
             // Assert
-            Assert.AreEqual("-", assessmentLayerTwoA);
+            Assert.IsNaN(assessmentLayerTwoA);
             mocks.VerifyAll();
         }
 
+        [Test]
+        public void AssessmentLayerTwoA_NoScenarios_ReturnsValue()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+
+            // Call
+            var assessmentLayerTwoA = failureMechanismSectionResult.AssessmentLayerTwoA;
+
+            // Assert
+            Assert.AreEqual((RoundedDouble)0.0, assessmentLayerTwoA);
+        }
+
+        [Test]
+        public void TotalContribution_Always_ReturnsTotalRelevantScenarioContribution()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+            
+            var mocks = new MockRepository();
+            var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)0.3);
+            
+            var calculationScenarioMock2 = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock2.Expect(cs => cs.IsRelevant).Return(true);
+            calculationScenarioMock2.Expect(cs => cs.Contribution).Return((RoundedDouble)0.5);
+            
+            var calculationScenarioMock3 = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock3.Expect(cs => cs.IsRelevant).Return(false);
+
+            mocks.ReplayAll();
+
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock);
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock2);
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock3);
+
+            // Call
+            var totalContribution = failureMechanismSectionResult.TotalContribution;
+
+            // Assert
+            Assert.AreEqual((RoundedDouble)0.8, totalContribution);
+            mocks.VerifyAll();
+        }
+
+        [Test]
+        public void AssessmentLayerTwoB_Always_ReturnsSetValue()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+            var assessmentLayerTwoBValue = (RoundedDouble) 3.0;
+
+            // Call
+            failureMechanismSectionResult.AssessmentLayerTwoB = assessmentLayerTwoBValue;
+
+            // Assert
+            Assert.AreEqual(assessmentLayerTwoBValue, failureMechanismSectionResult.AssessmentLayerTwoB);
+        }
+
+        [Test]
+        public void AssessmentLayerThree_Always_ReturnsSetValue()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+            var assessmentLayerThreeValue = (RoundedDouble)3.0;
+
+            // Call
+            failureMechanismSectionResult.AssessmentLayerThree = assessmentLayerThreeValue;
+
+            // Assert
+            Assert.AreEqual(assessmentLayerThreeValue, failureMechanismSectionResult.AssessmentLayerThree);
+        }
+
+        [Test]
+        public void CalculationScenarios_Always_ReturnsAddedCalculationScenarios()
+        {
+            // Setup
+            var section = CreateSection();
+            var failureMechanismSectionResult = new FailureMechanismSectionResult(section);
+
+            // Precondition
+            CollectionAssert.IsEmpty(failureMechanismSectionResult.CalculationScenarios);
+
+            var mocks = new MockRepository();
+            var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
+            var calculationScenarioMock2 = mocks.StrictMock<ICalculationScenario>();
+            var calculationScenarioMock3 = mocks.StrictMock<ICalculationScenario>();
+
+            mocks.ReplayAll();
+
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock);
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock2);
+            failureMechanismSectionResult.CalculationScenarios.Add(calculationScenarioMock3);
+
+            // Call
+            var scenarios = failureMechanismSectionResult.CalculationScenarios;
+
+            // Assert
+            CollectionAssert.AreEqual(new[] {calculationScenarioMock, calculationScenarioMock2, calculationScenarioMock3}, scenarios);
+            mocks.VerifyAll();
+        }
+
         private static FailureMechanismSection CreateSection()
         {
             var points = new[]
Index: Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/FailureMechanismResultViewTest.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/FailureMechanismResultViewTest.cs	(.../FailureMechanismResultViewTest.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Common/test/Ringtoets.Common.Forms.Test/Views/FailureMechanismResultViewTest.cs	(.../FailureMechanismResultViewTest.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -337,13 +337,14 @@
         }
 
         [Test]
-        public void FailureMechanismResultView_AssessmentLayerTwoANaN_ShowsErrorTooltip()
+        public void FailureMechanismResultView_TotalContributionNotHundred_ShowsErrorTooltip()
         {
             // Setup
             var mocks = new MockRepository();
             var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
-            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble) 0.3);
-            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble) 0.3).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble) 1000).Repeat.Any();
 
             mocks.ReplayAll();
 
@@ -364,6 +365,8 @@
 
                 // Assert
                 Assert.AreEqual("Bijdrage van de geselecteerde scenario's voor dit vak zijn opgeteld niet gelijk aan 100%", dataGridViewCell.ErrorText);
+                Assert.AreEqual(double.NaN.ToString(), formattedValue);
+                mocks.VerifyAll();
             }
         }
 
@@ -373,8 +376,9 @@
             // Setup
             var mocks = new MockRepository();
             var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
-            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0);
-            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true);
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble?) 1000).Repeat.Any();
 
             mocks.ReplayAll();
 
@@ -395,9 +399,136 @@
 
                 // Assert
                 Assert.AreEqual(string.Empty, dataGridViewCell.ErrorText);
+                Assert.AreEqual(string.Format("1/{0:N0}", calculationScenarioMock.Probability), formattedValue);
+                mocks.VerifyAll();
             }
         }
 
+        [Test]
+        public void FailureMechanismResultView_AssessmentLayerTwoANull_ShowsErrorTooltip()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.Probability).Return(null).Repeat.Any();
+
+            mocks.ReplayAll();
+
+            var rowIndex = 0;
+
+            using (var view = ShowFullyConfiguredFailureMechanismResultsView())
+            {
+                var sections = (List<FailureMechanismSectionResult>)view.Data;
+                sections[0].CalculationScenarios.Add(calculationScenarioMock);
+
+                var gridTester = new ControlTester("dataGridView");
+                var dataGridView = (DataGridView)gridTester.TheObject;
+
+                DataGridViewCell dataGridViewCell = dataGridView.Rows[rowIndex].Cells[assessmentLayerTwoAIndex];
+
+                // Call
+                var formattedValue = dataGridViewCell.FormattedValue; // Need to do this to fire the CellFormatting event.
+
+                // Assert
+                Assert.AreEqual("Niet alle berekeningen voor dit vak zijn uitgevoerd.", dataGridViewCell.ErrorText);
+                Assert.AreEqual("-", formattedValue);
+                mocks.VerifyAll();
+            }
+        }
+
+        [Test]
+        public void FailureMechanismResultView_AssessmentLayerTwoANaN_ShowsErrorTooltip()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble?) double.NaN).Repeat.Any();
+
+            mocks.ReplayAll();
+
+            var rowIndex = 0;
+
+            using (var view = ShowFullyConfiguredFailureMechanismResultsView())
+            {
+                var sections = (List<FailureMechanismSectionResult>)view.Data;
+                sections[0].CalculationScenarios.Add(calculationScenarioMock);
+
+                var gridTester = new ControlTester("dataGridView");
+                var dataGridView = (DataGridView)gridTester.TheObject;
+
+                DataGridViewCell dataGridViewCell = dataGridView.Rows[rowIndex].Cells[assessmentLayerTwoAIndex];
+
+                // Call
+                var formattedValue = dataGridViewCell.FormattedValue; // Need to do this to fire the CellFormatting event.
+
+                // Assert
+                Assert.AreEqual("Niet alle berekeningen voor dit vak hebben een geldige uitkomst.", dataGridViewCell.ErrorText);
+                Assert.AreEqual("-", formattedValue);
+                mocks.VerifyAll();
+            }
+        }
+
+        [Test]
+        public void FailureMechanismResultView_NoCalculationScenarios_DoesNotShowErrorTooltip()
+        {
+            // Setup
+            var rowIndex = 0;
+
+            using (ShowFullyConfiguredFailureMechanismResultsView())
+            {
+                var gridTester = new ControlTester("dataGridView");
+                var dataGridView = (DataGridView)gridTester.TheObject;
+
+                DataGridViewCell dataGridViewCell = dataGridView.Rows[rowIndex].Cells[assessmentLayerTwoAIndex];
+
+                // Call
+                var formattedValue = dataGridViewCell.FormattedValue; // Need to do this to fire the CellFormatting event.
+
+                // Assert
+                Assert.AreEqual(string.Empty, dataGridViewCell.ErrorText);
+                Assert.AreEqual("-", formattedValue);
+            }
+        }
+
+        [Test]
+        public void FailureMechanismResultView_AssessmentLayerTrueAndAssessmentLayerTwoAHasError_DoesNotShowError()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var calculationScenarioMock = mocks.StrictMock<ICalculationScenario>();
+            calculationScenarioMock.Expect(cs => cs.Contribution).Return((RoundedDouble)1.0).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.IsRelevant).Return(true).Repeat.Any();
+            calculationScenarioMock.Expect(cs => cs.Probability).Return((RoundedDouble?)double.NaN).Repeat.Any();
+
+            mocks.ReplayAll();
+
+            var rowIndex = 0;
+
+            using (var view = ShowFullyConfiguredFailureMechanismResultsView())
+            {
+                var sections = (List<FailureMechanismSectionResult>)view.Data;
+                sections[0].CalculationScenarios.Add(calculationScenarioMock);
+
+                var gridTester = new ControlTester("dataGridView");
+                var dataGridView = (DataGridView)gridTester.TheObject;
+
+                DataGridViewCell dataGridViewCell = dataGridView.Rows[rowIndex].Cells[assessmentLayerTwoAIndex];
+
+                // Call
+                dataGridView.Rows[rowIndex].Cells[assessmentLayerOneIndex].Value = true;
+                var formattedValue = dataGridViewCell.FormattedValue; // Need to do this to fire the CellFormatting event.
+
+                // Assert
+                Assert.AreEqual(string.Empty, dataGridViewCell.ErrorText);
+                Assert.AreEqual("-", formattedValue);
+                mocks.VerifyAll();
+            }
+        }
+
         private const int nameColumnIndex = 0;
         private const int assessmentLayerOneIndex = 1;
         private const int assessmentLayerTwoAIndex = 2;
Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingCalculationScenario.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingCalculationScenario.cs	(.../PipingCalculationScenario.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/PipingCalculationScenario.cs	(.../PipingCalculationScenario.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -49,11 +49,11 @@
 
         public RoundedDouble Contribution { get; set; }
 
-        public RoundedDouble Probability
+        public RoundedDouble? Probability
         {
             get
             {
-                return SemiProbabilisticOutput != null ? SemiProbabilisticOutput.PipingProbability : (RoundedDouble) double.NaN;
+                return SemiProbabilisticOutput != null ? SemiProbabilisticOutput.PipingProbability : (RoundedDouble?) null;
             }
         }
     }
Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingCalculationScenarioTest.cs
===================================================================
diff -u -r8323c6cbe3f292646a254938161e17c42d13d10c -rf7a9f7239374705ff1d732e9666c0cb62ebaafd0
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingCalculationScenarioTest.cs	(.../PipingCalculationScenarioTest.cs)	(revision 8323c6cbe3f292646a254938161e17c42d13d10c)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingCalculationScenarioTest.cs	(.../PipingCalculationScenarioTest.cs)	(revision f7a9f7239374705ff1d732e9666c0cb62ebaafd0)
@@ -42,7 +42,7 @@
             Assert.AreSame(semiProbabilisticInputParameters, scenario.SemiProbabilisticParameters);
             Assert.IsTrue(scenario.IsRelevant);
             Assert.AreEqual(new RoundedDouble(0), scenario.Contribution);
-            Assert.IsNaN(scenario.Probability);
+            Assert.IsNull(scenario.Probability);
         }
 
         [Test]
@@ -103,7 +103,7 @@
         }
 
         [Test]
-        public void Probability_PipingOutputNull_ReturnsNaN()
+        public void Probability_PipingOutputNull_ReturnsNull()
         {
             // Setup
             var generalInputParameters = new GeneralPipingInput();
@@ -115,7 +115,24 @@
             var propability = scenario.Probability;
 
             // Assert
-            Assert.IsNaN(propability);
+            Assert.IsNull(propability);
         }
+
+        [Test]
+        public void Probabilty_ScenarioInvalid_ReturnsNaN()
+        {
+            // Setup
+            var generalInputParameters = new GeneralPipingInput();
+            var semiProbabilisticInputParameters = new SemiProbabilisticPipingInput();
+
+            var scenario = new PipingCalculationScenario(generalInputParameters, semiProbabilisticInputParameters);
+            scenario.SemiProbabilisticOutput = new PipingSemiProbabilisticOutput(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, double.NaN, 0, 0);
+
+            // Call
+            var propability = scenario.Probability;
+
+            // Assert
+            Assert.IsNaN(propability.Value);
+        }
     }
 }
\ No newline at end of file