Created
January 15, 2013 06:21
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2つのサイコロの出目の和について、標準偏差(sigma)が全体の68%ぐらいであるかどうかの検証コード
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#!/bin/env ruby | |
# encoding: utf-8 | |
# Author: kimoto | |
class Array | |
def sum | |
self.inject(0){|total,i| | |
total += i | |
} | |
end | |
def avg | |
self.sum / self.size | |
end | |
def sigma | |
avg = self.avg | |
diff = self.map{ |i| | |
(i - avg) ** 2 | |
} | |
Math.sqrt(diff.sum / diff.size) | |
end | |
end | |
def dice | |
[1,2,3,4,5,6].sample | |
end | |
puts "rand() + rand() test" | |
r = [] | |
n = 1000 | |
d = {} | |
n.times{ | |
n = dice + dice | |
r << n | |
d[n] ||= 0 | |
d[n] += 1 | |
} | |
d.keys.sort.each{ |k| | |
puts "#{k} => #{d[k]}" | |
} | |
# 平均値の算出 | |
p r.avg | |
# => 7 | |
# 標準偏差が判明(だいたい2.4ぐらい) | |
p r.sigma | |
# => 2.23606797749979 | |
total = 0 | |
d.each{ |k,v| total += v } | |
# 標準偏差の1x範囲に68%が収まるかどうかの確認 | |
min = r.avg - r.sigma.to_i | |
max = r.avg + r.sigma.to_i | |
puts "sigma1: #{min} <= #{max}" | |
sum = 0 | |
(min .. max).each{ |i| | |
sum += d[i] if d.has_key?(i) | |
} | |
p sum.to_f / total.to_f | |
# => 0.634 (だいたいあってる) | |
# 標準偏差の2x範囲に95%が収まるかどうかの確認 | |
min = r.avg - (r.sigma.to_i * 2) | |
max = r.avg + (r.sigma.to_i * 2) | |
puts "sigma2: #{min} <= #{max}" | |
sum = 0 | |
(min .. max).each{ |i| | |
sum += d[i] if d.has_key?(i) | |
} | |
p sum.to_f / total.to_f | |
# => 0.917 (だいたいあってる) | |
# 標準偏差の3x範囲に99%がおさまるかどうかの確認 | |
min = r.avg - (r.sigma.to_i * 3) | |
max = r.avg + (r.sigma.to_i * 3) | |
puts "sigma3: #{min} <= #{max}" | |
sum = 0 | |
(min .. max).each{ |i| | |
sum += d[i] if d.has_key?(i) | |
} | |
p sum.to_f / total.to_f | |
# => 1 (だいたいあってるけどちゃんとしてるかな) |
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