diff --git a/ApplicationCode/ReservoirDataModel/ReservoirDataModel_UnitTests/RigStatisticsMath-Test.cpp b/ApplicationCode/ReservoirDataModel/ReservoirDataModel_UnitTests/RigStatisticsMath-Test.cpp
index e8e04cf3b3..1be15da9bc 100644
--- a/ApplicationCode/ReservoirDataModel/ReservoirDataModel_UnitTests/RigStatisticsMath-Test.cpp
+++ b/ApplicationCode/ReservoirDataModel/ReservoirDataModel_UnitTests/RigStatisticsMath-Test.cpp
@@ -175,10 +175,8 @@ TEST(RigStatisticsMath, InterpolatedPercentiles)
     pValPos.push_back(90);
     std::vector<double> pVals = RigStatisticsMath::calculateInterpolatedPercentiles(values, pValPos);
 
-    /*
-    EXPECT_DOUBLE_EQ( -76092.8157632591000, pVals[0]);
-    EXPECT_DOUBLE_EQ( 2788.2723335651900  , pVals[1]);
-    EXPECT_DOUBLE_EQ( 6391.979999097290   , pVals[2]);
-    EXPECT_DOUBLE_EQ( 96161.7546348456000 , pVals[3]);
-    */
+    EXPECT_DOUBLE_EQ( -72278.340409937548,  pVals[0]);
+    EXPECT_DOUBLE_EQ(  -2265.6006907818719, pVals[1]);
+    EXPECT_DOUBLE_EQ(   6391.9799990972897, pVals[2]);
+    EXPECT_DOUBLE_EQ(  93073.49128098879,   pVals[3]);
 }
diff --git a/ApplicationCode/ReservoirDataModel/RigStatisticsMath.cpp b/ApplicationCode/ReservoirDataModel/RigStatisticsMath.cpp
index 350115dfd7..a6148b98ee 100644
--- a/ApplicationCode/ReservoirDataModel/RigStatisticsMath.cpp
+++ b/ApplicationCode/ReservoirDataModel/RigStatisticsMath.cpp
@@ -142,22 +142,22 @@ std::vector<double> RigStatisticsMath::calculateInterpolatedPercentiles(const st
         {
             double pVal = HUGE_VAL;
 
-            double doubleIndex = sortedValues.size() * fabs(pValPositions[i]) / 100.0;
+            double doubleIndex = (sortedValues.size() - 1) * fabs(pValPositions[i]) / 100.0;
 
             size_t lowerValueIndex = static_cast<size_t>(floor(doubleIndex));
             size_t upperValueIndex = lowerValueIndex + 1;
 
-            if (lowerValueIndex >= sortedValues.size() ) lowerValueIndex = sortedValues.size() - 1;
-            if (upperValueIndex >= sortedValues.size() ) upperValueIndex = sortedValues.size() - 1;
+            double upperValueWeight = doubleIndex - lowerValueIndex;
+            assert(upperValueWeight < 1.0);
 
-            double upperValueWeight = 1.0;
-            if (lowerValueIndex != upperValueIndex)
+            if (upperValueIndex < sortedValues.size())
             {
-                upperValueWeight = doubleIndex - lowerValueIndex;
-                assert(upperValueWeight < 1.0);
+                pVal = (1.0 - upperValueWeight) * sortedValues[lowerValueIndex] + upperValueWeight * sortedValues[upperValueIndex];
+            }
+            else
+            {
+                pVal = sortedValues[lowerValueIndex];
             }
-
-            pVal = (1.0 - upperValueWeight) * sortedValues[lowerValueIndex] + upperValueWeight * sortedValues[upperValueIndex];
             percentiles[i] = pVal;
         }
     }