this is good for testing Quiz#statistics performance

generate_big_quiz.rb

COURSE_ID = 5  # replace this with id of course with many (>=500) students
               # generating a large course is left as an exercise to the reader

course = Course.find(COURSE_ID)

# generate quiz
q = course.quizzes.create! :title => "Big Quiz"

eval(File.read 'quiz_questions.txt').each_with_index do |(question, as), i|
  answers = as.map.with_index { |a, j|
    ["answer_#{i+j}", {:answer_text => a, :id => i + j, :answer_weight => 0}]
  }
  answers[rand answers.size][1][:answer_weight] = 100

  q.quiz_questions.create! :question_data => {
    :question_type => "multiple_choice_question", 
    :question_name => "Question #{i+1}",
    :question_text => question,
    :points_possible => 1,
    :answers => answers
  }
end

q.points_possible = q.quiz_questions.map {
  |qq| qq.question_data[:points_possible]
}.sum
q.generate_quiz_data
q.published_at = Time.now
q.publish!


# generate submissions
course.students.order(:id).each do |student|
  puts "generating submission for #{student.name}"
  qs = q.generate_submission(student)
  submission_data = {}
  expected_score = rand(0.6..1)

  qs.quiz_data.each do |question|
    prob = rand
    next if prob <= 0.1 # skipped

    correct, incorrect = question[:answers].partition { |a| a[:weight] == 100 }

    answer = rand < expected_score ?
                   correct.first :
                   incorrect.first
    submission_data["question_#{question[:id]}"] = answer[:id].to_s
  end

  qs.mark_completed
  qs.submission_data = submission_data
  qs.grade_submission
end