def online_variance(data):
    '\n        A numerically stable algorithm for calculating variance\n        http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#On-line_algorithm\n    '
    n = 0
    mean = 0
    M2 = 0
    for x in data:
        n = (n + 1)
        delta = (x - mean)
        mean = (mean + (delta / n))
        M2 = (M2 + (delta * (x - mean)))
    variance_n = (M2 / n)
    variance = (M2 / (n - 1))
    return (variance, variance_n)
A numerically stable algorithm for calculating variance
http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#On-line_algorithm
def online_variance(data):
    '\n        A numerically stable algorithm for calculating variance\n        http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#On-line_algorithm\n    '
    n = 0
    mean = 0
    M2 = 0
    for x in data:
        n = (n + 1)
        delta = (x - mean)
        mean = (mean + (delta / n))
        M2 = (M2 + (delta * (x - mean)))
    variance_n = (M2 / n)
    variance = (M2 / (n - 1))
    return (variance, variance_n)