从 1% 的样本中评估总体的平均值

calculate_kodomo.rb

#!/usr/bin/env ruby
#生成 10_000 个呈正态分布的范围在0-4之间的随机数
#计算他们的平均值

#从中随机抽取100个数
 #通过有放回重抽法尝试 10_000 次
  #每次抽 100 个数
  #计算这100个数的平均值
 #计算这 10_000 次的平均值

#以上步骤尝试100次
module Solution
  extend self
  def go
    all = []
    10_000.times { all << get_from_nd(2, 0.2) }
    # aver_all = all.reduce(:+).to_f / 10_000
    count = 0
    100.times do
      pick_up_100 = pick_non_repeat(all, 100)
      aver_100_arr = []

      10_000.times do
        random_100 = []
        100.times do
          random_100 << pick_up_100[rand(100)]
        end
        aver_100_arr << random_100.reduce(:+).to_f / random_100.length
      end
      if (aver_100_arr.reduce(:+).to_f / aver_100_arr.length - 2).abs > 0.05
        count += 1
      end
    end
  count
  end

  def pick_non_repeat(arr, count)
    range = arr.length
    r = []
    i = 0
    while i <= count
      gen = rand(range)
      if !r.include? gen
        r.push gen
        i += 1
      end
    end
    r.map { |i| arr[i] }
  end

  def get_from_nd(mean, std_dev)
    mean + random_nd * std_dev
  end

  def random_nd
    w = 0.0
    u = 0.0
    v = 0.0
    c = 0.0
    while w ==0.0 || w >=1.0
      u = rand * 2 - 1.0
      v = rand * 2 - 1.0
      w = u * u + v * v
    end
    c = Math.sqrt(-2 * Math.log(w) / w)

    u * c
  end
end

puts Solution.go