Performs Welford's online algorithm for updating variance. Can also put another VarianceAccumulator of the same type, which uses the parallel algorithm from Chan et al., described above.

Calculates variance using E(x^^2) - E(x)^2 (alowing for adjustments for population/sample variance). This algorithm can be numerically unstable.

Calculates variance using a two-pass algorithm whereby the input is first centered and then the sum of squares is calculated from that.

Calculates variance assuming the mean of the dataseries is zero.