分数和红宝石中的z分数 [英] z-score to probability and vice verse in ruby

问题描述

如何使用红宝石将z分数转换为概率?

How can I convert z-score to probability using ruby?

示例:

z_score = 0
probability should be 0.5

z_score = 1.76
probability should be 0.039204

推荐答案

根据此 https://stackoverflow.com/a/16197404/1062711 帖子，这是从z得分为您提供p proba的函数

According to this https://stackoverflow.com/a/16197404/1062711 post, here is the function that give you the p proba from the z score

def getPercent(z)
  return 0 if z < -6.5
  return 1 if z > 6.5

  factk = 1
  sum = 0
  term = 1
  k = 0

  loopStop = Math.exp(-23)
  while term.abs > loopStop do
      term = 0.3989422804 * ((-1)**k) * (z**k) / (2*k+1) / (2**k) * (z**(k+1)) /factk
      sum += term
      k += 1
      factk *= k
  end

  sum += 0.5
  1-sum
end

puts getPercent(1.76)

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