added standard deviations

app/controllers/execution_environments_controller.rb

@@ -31,7 +31,7 @@ class ExecutionEnvironmentsController < ApplicationController
 
   def working_time_query
     """
-      SELECT exercise_id, avg(working_time) as average_time
+      SELECT exercise_id, avg(working_time) as average_time, stddev_samp(extract('epoch' from working_time)) * interval '1 second' as stddev_time
       FROM
         (
       SELECT user_id,
@@ -62,6 +62,7 @@ class ExecutionEnvironmentsController < ApplicationController
       COUNT(DISTINCT user_id) AS users,
       AVG(score) AS average_score,
       MAX(score) AS maximum_score,
+      stddev_samp(score) as stddev_score,
       CASE
         WHEN MAX(score)=0 THEN 0
         ELSE 100 / MAX(score) * AVG(score)

app/views/execution_environments/statistics.html.slim

@@ -4,19 +4,22 @@ h1 = @execution_environment
   table.table.table-striped.sortable
     thead
       tr
-        - ['.exercise', '.users', '.score', '.maximum_score', '.percentage_correct', '.runs', '.worktime'].each do |title|
+        - ['.exercise', '.users', '.score', '.maximum_score', '.stddev_score', '.percentage_correct', '.runs', '.worktime', '.stddev_worktime'].each do |title|
           th.header = t(title)
     tbody
       - @execution_environment.exercises.each do |exercise|
         - us = user_statistics[exercise.id]
-        - if not us then us = {"users" => 0, "average_score" => 0.0, "maximum_score" => 0, "percent_correct" => nil, "average_submission_count" => 0}
+        - if not us then us = {"users" => 0, "average_score" => 0.0, "maximum_score" => 0, "stddev_score" => 0.0, "percent_correct" => nil, "average_submission_count" => 0}
         - wts = working_time_statistics[exercise.id]
         - if wts then average_time = wts["average_time"] else 0
+        - if wts then stddev_time = wts["stddev_time"] else 0
         tr
           td = link_to exercise.title, controller: "exercises", action: "statistics", id: exercise.id
           td = us["users"]
           td = us["average_score"]
           td = us["maximum_score"]
+          td = us["stddev_score"]
           td = us["percent_correct"]
           td = us["average_submission_count"]
           td = average_time
+          td = stddev_time

config/locales/de.yml

@@ -171,6 +171,8 @@ de:
       exercise: Übung
       users: Anzahl (externer) Nutzer
       score: Durchschnittliche Punktzahl
+      stddev_score: stdabw (Punktzahl)
+      stddev_worktime: stdabw (Arbeitszeit)
       maximum_score: Maximale Punktzahl
       percentage_correct: Prozent Korrekt
       runs: Durchschnittliche Anzahl von Versuchen

config/locales/en.yml

@@ -171,6 +171,8 @@ en:
       exercise: Exercise
       users: (External) Users Count
       score: Average Score
+      stddev_score: stddev (score)
+      stddev_worktime: stddev (working time)
       maximum_score: Maximum Score
       percentage_correct: Percentage Correct
       runs: Average Number of Runs