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Maple users may notice unexpected results when calculating standard deviations with weights.

This is because the notion of weights used by Maple is not exactly the commonly used notion of repeated measurements.

Maple uses the NAG library from the Numerical Algorithms Group to compute the standard deviation in the presence of weights. The formula that is used is given in their documentation: https://www.nag.com/numeric/cl/nagdoc_cl25/pdf/g01/g01aac.pdf.

 

NULL

> 

restart
> 

with(Statistics)
> 

V := `<,>`(seq(i, i = 57 .. 77), undefined)

_rtable[36893489755601713980]

 (1)
> 

W := `<,>`(2, 4, 14, 41, 83, 169, 394, 669, 990, 1223, 1329, 1230, 1063, 646, 392, 202, 79, 32, 16, 5, 2, 5)
> 

StandardDeviation(V, weights = W)

HFloat(HFloat(undefined))

 (2)
> 

StandardDeviation(V, weights = W, ignore = true)

HFloat(2.7274213984819053)

 (3)

NULL

Download standard-deviation-weights-help-example.mw
standard-deviation nag weight statistics

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