diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index 0f691fde..0a266532 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -75,6 +75,30 @@ class Exercise < ActiveRecord::Base
     """
   end
 
+  def getQuantiles(quantiles)
+    quantiles_str = "[" + quantiles.join(",") + "]"
+    result = self.class.connection.execute("""
+      SELECT unnest(PERCENTILE_CONT(ARRAY#{quantiles_str}) WITHIN GROUP (ORDER BY working_time))
+      FROM
+          (
+            SELECT user_id,
+                   sum(working_time_new) AS working_time
+            FROM
+              (SELECT user_id,
+                      CASE WHEN working_time >= '0:30:00' THEN '0' ELSE working_time END AS working_time_new
+               FROM
+                  (SELECT user_id,
+                          id,
+                          (created_at - lag(created_at) OVER (PARTITION BY user_id
+                                                              ORDER BY created_at)) AS working_time
+                  FROM submissions
+                  WHERE exercise_id=69) AS foo) AS bar
+            GROUP BY user_id
+      ) AS foo
+    """)
+    quantiles.each_with_index.map{|q,i| [q, Time.parse(result[i]["unnest"]).seconds_since_midnight]}.to_h
+  end
+
   def retrieve_working_time_statistics
     @working_time_statistics = {}
     self.class.connection.execute(user_working_time_query).each do |tuple|
diff --git a/app/models/proxy_exercise.rb b/app/models/proxy_exercise.rb
index 2efa8962..678aeb4a 100644
--- a/app/models/proxy_exercise.rb
+++ b/app/models/proxy_exercise.rb
@@ -54,11 +54,24 @@ class ProxyExercise < ActiveRecord::Base
       ]
     end
 
+    def scoring_matrix_quantiles
+      [0.2,0.4,0.6,0.8]
+    end
+
     def score(user, ex)
       points_ratio =  ex.maximum_score(user) / ex.maximum_score.to_f
+      points_ratio_index = points_ratio.to_i
       working_time_user = Time.parse(ex.average_working_time_for_only(user.id) || "00:00:00")
       scoring_matrix = scoring_matrix
-
+      quantiles_working_time = ex.getQuantiles(scoring_matrix_quantiles)
+      quantile_index = quantile_time.size
+      quantiles_working_time.each_with_index do |quantile_time, i|
+        if working_time_user <= quantile_time
+          quantile_index = i
+          break
+        end
+      end
+      scoring_matrix[points_ratio_index][quantile_index]
     end
 
     def getRelativeKnowledgeLoss(user, execises)
@@ -66,11 +79,11 @@ class ProxyExercise < ActiveRecord::Base
       topic_knowledge_loss_user = Tag.all.map{|t| [t, 0]}.to_h
       topic_knowledge_max = Tag.all.map{|t| [t, 0]}.to_h
       execises.each do |ex|
-        score = score(user, ex)
+        user_score_factor = score(user, ex)
         ex.tags.each do |t|
           tag_ratio = ex.exercise_tags.where(tag: t).factor / ex.exercise_tags.inject(0){|sum, et| sum += et.factor }
           topic_knowledge = ex.expected_difficulty * tag_ratio
-          topic_knowledge_loss_user[t] += (1-score) * topic_knowledge
+          topic_knowledge_loss_user[t] += (1 - user_score_factor) * topic_knowledge
           topic_knowledge_max[t] += topic_knowledge
         end
       end