Mean And Stddev

MeanAndStddev

import math

class MeanAndStddev:
    def __init__(self):
        self.values = [];
    def append(self, val):
        self.values.append(val * 1.0)
    def mean(self):
        sumValue = 0
        for a in self.values:
            sumValue += a
        return sumValue/len(self.values)
    def variance(self):
        mean = self.mean()
        sumMean = 0.0
        for a in self.values:
            sumMean += (a - mean) * (a - mean)
        return sumMean / len(self.values)
    def stddev(self):
        return math.sqrt(self.variance())
    def standardScore(self, index):
	return ((10.0 * (self.values[index] - self.mean()))/ self.stddev()) + 50.0