## 5.26. Variance and Standard DeviationThe variance of a set of data is a measure of how "spread out" the values are. (Here we do not distinguish between biased and unbiased estimates.) The standard deviation, usually represented by a sigma (σ) is simply the square root of the variance. data = [2, 3, 2, 2, 3, 4, 5, 5, 4, 3, 4, 1, 2] def variance(x) m = mean(x) sum = 0.0 x.each {|v| sum += (v-m)**2 } sum/x.size end def sigma(x) Math.sqrt(variance(x)) end puts variance(data) # 1.461538462 puts sigma(data) # 1.20894105 Note that the |

The Ruby Way, Second Edition: Solutions and Techniques in Ruby Programming (2nd Edition)

ISBN: 0672328844

EAN: 2147483647

EAN: 2147483647

Year: 2004

Pages: 269

Pages: 269

Authors: Hal Fulton

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