Monty Hall Statistics simulation script.

monty_hall_simulation.rb

def random_between_1_and_3
  (rand * 3).ceil
end

file = File.open('results.csv', 'w')

file.puts 'car, first_choice, expose, second_choice, win, switch, switch_and_win, stay_and_win'

1_000_000.times do

  car = random_between_1_and_3

  first_choice = random_between_1_and_3

  expose = [1,2,3].tap { |a| a.delete(car)}.shuffle.first

  second_choice = [1,2,3].tap { |a| a.delete(expose)}.shuffle.first

  win = second_choice == car ? 'YES' : ''

  switch = second_choice != first_choice ? 'YES' : ''

  switch_and_win = win == 'YES' && switch == 'YES' ? 'YES' : ''

  stay_and_win = win == 'YES'  && switch != 'YES'  ? 'YES' : ''

  file.puts [car, first_choice, expose, second_choice, win, switch, switch_and_win, stay_and_win].join(',')
end

file.close

# Results:
# switch and win: 333203
# stay and win:   166179