diff --git a/app/assets/javascripts/editor/editor.js.erb b/app/assets/javascripts/editor/editor.js.erb
index 2c2b8011..9deff0d6 100644
--- a/app/assets/javascripts/editor/editor.js.erb
+++ b/app/assets/javascripts/editor/editor.js.erb
@@ -323,9 +323,7 @@ configureEditors: function () {
     var button = $('#requestComments');
     button.prop('disabled', true);
     button.on('click', function () {
-      if ($('#editor').data('show-interventions') == true){
-        $('#rfc_intervention_text').hide()
-      }
+      $('#rfc_intervention_text').hide()
       $('#comment-modal').modal('show');
     });
 
@@ -578,64 +576,63 @@ configureEditors: function () {
      * interventions
      * */
     initializeInterventionTimer: function() {
-        $.ajax({
-            data: {
-                exercise_id: $('#editor').data('exercise-id'),
-                user_id: $('#editor').data('user-id')
-            },
-            dataType: 'json',
-            method: 'GET',
-            // get working times for this exercise
-            url: $('#editor').data('working-times-url'),
-            success: function (data) {
-                var percentile75 = data['working_time_75_percentile'];
-                var accumulatedWorkTimeUser = data['working_time_accumulated'];
+        if ($('#editor').data('rfc-interventions') == true || $('#editor').data('break-interventions') == true) { // split in break or rfc intervention
+            $.ajax({
+                data: {
+                    exercise_id: $('#editor').data('exercise-id'),
+                    user_id: $('#editor').data('user-id')
+                },
+                dataType: 'json',
+                method: 'GET',
+                // get working times for this exercise
+                url: $('#editor').data('working-times-url'),
+                success: function (data) {
+                    var percentile75 = data['working_time_75_percentile'];
+                    var accumulatedWorkTimeUser = data['working_time_accumulated'];
 
-                var timeUntilBreak = 20 * 60 * 1000;
-                var minTimeUntilAskQuestion = 15 * 60 * 1000;
+                    var minTimeIntervention = 10 * 60 * 1000;
 
-                if ((accumulatedWorkTimeUser - percentile75) > 0) {
-                    // working time is already over 75 percentile
-                    var timeUntilAskQuestion = minTimeUntilAskQuestion;
-                } else {
-                    // working time is less than 75 percentile
-                    // ensure we give user at least 10 minutes before we bother the user
-                    var timeUntilAskForRFC = (percentile75 - accumulatedWorkTimeUser) > minTimeUntilAskQuestion ? (percentile75 - accumulatedWorkTimeUser) : minTimeUntilAskQuestion;
+                    if ((accumulatedWorkTimeUser - percentile75) > 0) {
+                        // working time is already over 75 percentile
+                        var timeUntilIntervention = minTimeIntervention;
+                    } else {
+                        // working time is less than 75 percentile
+                        // ensure we give user at least minTimeIntervention before we bother the user
+                        var timeUntilIntervention = Math.max(percentile75 - accumulatedWorkTimeUser, minTimeIntervention);
+                    }
+                    if ($('#editor').data('break-interventions')){
+                        setTimeout(function () {
+                            $('#break-intervention-modal').modal('show');
+                            $.ajax({
+                                data: {
+                                    intervention_type: 'BreakIntervention'
+                                },
+                                dataType: 'json',
+                                type: 'POST',
+                                url: $('#editor').data('intervention-save-url')
+                            });
+                        }, timeUntilIntervention);
+                    } else if ($('#editor').data('rfc-interventions')) {
+                        setTimeout(function () {
+                            var button = $('#requestComments');
+                            // only show intervention if user did not requested for a comment already
+                            if (!button.prop('disabled')) {
+                                $('#rfc_intervention_text').show();
+                                $('#comment-modal').modal('show');
+                                $.ajax({
+                                    data: {
+                                        intervention_type: 'QuestionIntervention'
+                                    },
+                                    dataType: 'json',
+                                    type: 'POST',
+                                    url: $('#editor').data('intervention-save-url')
+                                });
+                            };
+                        }, timeUntilIntervention);
+                    }
                 }
-
-                // if notifications are too close to each other, ensure some time differences between them
-                if (Math.abs(timeUntilAskForRFC - timeUntilBreak) < 5 * 1000 * 60){
-                    timeUntilBreak = timeUntilBreak * 2;
-                }
-
-                setTimeout(function() {
-                    $('#break-intervention-modal').modal('show');
-                    $.ajax({
-                        data: {
-                            intervention_type: 'BreakIntervention'
-                        },
-                        dataType: 'json',
-                        type: 'POST',
-                        url: $('#editor').data('intervention-save-url')});
-                }, timeUntilBreak);
-
-
-                setTimeout(function() {
-                    var button = $('#requestComments');
-                    if (!button.prop('disabled')){
-                        $('#rfc_intervention_text').show();
-                        $('#comment-modal').modal('show');
-                        $.ajax({
-                            data: {
-                                intervention_type: 'QuestionIntervention'
-                            },
-                            dataType: 'json',
-                            type: 'POST',
-                            url: $('#editor').data('intervention-save-url')});
-                    };
-                }, timeUntilAskForRFC);
-            }
-        });
+            });
+        }
     },
 
     initializeSearchButton: function(){
@@ -671,9 +668,7 @@ configureEditors: function () {
     this.initializeDescriptionToggle();
     this.initializeSideBarTooltips();
     this.initializeTooltips();
-    if ($('#editor').data('show-interventions') == true){
-        this.initializeInterventionTimer();
-    }
+    this.initializeInterventionTimer();
     this.initializeSearchButton();
     this.initPrompt();
     this.renderScore();
diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index 25361125..4a643a5d 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -21,7 +21,7 @@ class ExercisesController < ApplicationController
   private :authorize!
 
   def max_intervention_count
-    3
+    2
   end
 
 
@@ -168,7 +168,15 @@ class ExercisesController < ApplicationController
     user_got_enough_interventions = UserExerciseIntervention.where(exercise: @exercise, user: current_user).count >= max_intervention_count
     is_java_course = @course_token && @course_token.eql?(java_course_token)
 
-    @show_interventions = (!is_java_course || user_got_enough_interventions) ? "false" : "true"
+    user_intervention_group = UserGroupSeparator.getInterventionGroup(current_user)
+
+    case user_intervention_group
+      when :no_intervention
+      when :break_intervention
+        @show_break_interventions = (!is_java_course || user_got_enough_interventions) ? "false" : "true"
+      when :rfc_intervention
+        @show_rfc_interventions = (!is_java_course || user_got_enough_interventions) ? "false" : "true"
+    end
 
     @search = Search.new
     @search.exercise = @exercise
diff --git a/app/models/proxy_exercise.rb b/app/models/proxy_exercise.rb
index 11b5a545..a425b91b 100644
--- a/app/models/proxy_exercise.rb
+++ b/app/models/proxy_exercise.rb
@@ -53,28 +53,43 @@ class ProxyExercise < ActiveRecord::Base
     end
 
     def find_matching_exercise(user)
-      exercises_user_has_accessed = user.submissions.where("cause IN ('submit','assess')").map{|s| s.exercise}.uniq
-      tags_user_has_seen = exercises_user_has_accessed.map{|ex| ex.tags}.uniq.flatten
-      Rails.logger.debug("exercises_user_has_accessed #{exercises_user_has_accessed.map{|e|e.id}.join(",")}")
+      user_group = UserGroupSeparator.getProxyExerciseGroup(user)
+      case user_group
+        when :dummy_assigment
+          rec_ex = select_easiest_exercise(exercises)
+          @reason[:reason] = "dummy group"
+          Rails.logger.debug("assigned user to dummy group, and gave him exercise: #{rec_ex.title}")
+          rec_ex
+        when :random_assigment
+          @reason[:reason] = "random group"
+          rec_ex = exercises.shuffle.first
+          Rails.logger.debug("assigned user to random group, and gave him exercise: #{rec_ex.title}")
+          rec_ex
+        when :recommended_assignment
+          exercises_user_has_accessed = user.submissions.where("cause IN ('submit','assess')").map{|s| s.exercise}.uniq.compact
+          tags_user_has_seen = exercises_user_has_accessed.map{|ex| ex.tags}.uniq.flatten
+          Rails.logger.debug("exercises_user_has_accessed #{exercises_user_has_accessed.map{|e|e.id}.join(",")}")
 
-      # find execises
-      potential_recommended_exercises = []
-      exercises.each do |ex|
-        ## find exercises which have only tags the user has already seen
-        if (ex.tags - tags_user_has_seen).empty?
-          potential_recommended_exercises << ex
-        end
-      end
-      Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.map{|e|e.id}}")
-      # if all exercises contain tags which the user has never seen, recommend easiest exercise
-      if potential_recommended_exercises.empty?
-        Rails.logger.debug("matched easiest exercise in pool")
-        @reason[:reason] = "easiest exercise in pool. empty potential exercises"
-        select_easiest_exercise(exercises)
-      else
-        recommended_exercise = select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
-        recommended_exercise
+          # find execises
+          potential_recommended_exercises = []
+          exercises.each do |ex|
+            ## find exercises which have only tags the user has already seen
+            if (ex.tags - tags_user_has_seen).empty?
+              potential_recommended_exercises << ex
+            end
+          end
+          Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.map{|e|e.id}}")
+          # if all exercises contain tags which the user has never seen, recommend easiest exercise
+          if potential_recommended_exercises.empty?
+            Rails.logger.debug("matched easiest exercise in pool")
+            @reason[:reason] = "easiest exercise in pool. empty potential exercises"
+            select_easiest_exercise(exercises)
+          else
+            recommended_exercise = select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
+            recommended_exercise
+          end
       end
+
     end
     private :find_matching_exercise
 
diff --git a/app/views/exercises/_editor.html.slim b/app/views/exercises/_editor.html.slim
index 5b3c3478..4291028f 100644
--- a/app/views/exercises/_editor.html.slim
+++ b/app/views/exercises/_editor.html.slim
@@ -1,8 +1,9 @@
 - external_user_external_id = @current_user.respond_to?(:external_id) ? @current_user.external_id : '' #'tests' #(@current_user.uuid.present? ? @current_user.uuid : '')
 - external_user_id = @current_user.respond_to?(:external_id) ? @current_user.id : '' #'tests' #(@current_user.uuid.present? ? @current_user.uuid : '')
 - consumer_id = @current_user.respond_to?(:external_id) ? @current_user.consumer_id : '' #'tests' #(@current_user.uuid.present? ? @current_user.uuid : '')
-- show_interventions = @show_interventions || "false"
-#editor.row data-exercise-id=exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout',  permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-errors-url=execution_environment_errors_path(exercise.execution_environment) data-submissions-url=submissions_path data-user-id=@current_user.id data-user-external-id=external_user_external_id data-working-times-url=working_times_exercise_path data-intervention-save-url=intervention_exercise_path data-show-interventions=show_interventions data-course_token=@course_token data-search-save-url=search_exercise_path
+- show_break_interventions = @show_break_interventions || "false"
+- show_rfc_interventions = @show_rfc_interventions || "false"
+#editor.row data-exercise-id=exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout',  permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-errors-url=execution_environment_errors_path(exercise.execution_environment) data-submissions-url=submissions_path data-user-id=@current_user.id data-user-external-id=external_user_external_id data-working-times-url=working_times_exercise_path data-intervention-save-url=intervention_exercise_path data-rfc-interventions=show_rfc_interventions data-break-interventions=show_break_interventions data-course_token=@course_token data-search-save-url=search_exercise_path
   div id="sidebar" class=(@exercise.hide_file_tree ? 'sidebar-col-collapsed' : 'sidebar-col') = render('editor_file_tree', exercise: @exercise, files: @files)
   div id='output_sidebar' class='output-col-collapsed' = render('exercises/editor_output', external_user_id: external_user_id, consumer_id: consumer_id )
   div id='frames' class='editor-col'
diff --git a/lib/user_group_separator.rb b/lib/user_group_separator.rb
new file mode 100644
index 00000000..320cce96
--- /dev/null
+++ b/lib/user_group_separator.rb
@@ -0,0 +1,27 @@
+class UserGroupSeparator
+
+  # seperates user into 30% no intervention, 30% break intervention, 40% rfc intervention
+  def self.getInterventionGroup(user)
+    lastDigitId = user.id % 10
+    if lastDigitId < 3 # 0,1,2
+      :no_intervention
+    elsif lastDigitId < 6 # 3,4,5
+      :break_intervention
+    else # 6,7,8,9
+      :rfc_intervention
+    end
+  end
+
+  # seperates user into 20% dummy assignment, 20% random assignemnt, 60% recommended assignment
+  def self.getProxyExerciseGroup(user)
+    lastDigitCreatedAt = user.created_at.to_i % 10
+    if lastDigitCreatedAt < 2 # 0,1
+      :dummy_assigment
+    elsif lastDigitCreatedAt < 4 # 2,3
+      :random_assigment
+    else # 4,5,6,7,8,9
+      :recommended_assignment
+    end
+  end
+
+end
\ No newline at end of file