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:Well, algorithms I and III only scan the list of data once, whereas both versions of algorithm II scan it twice. Hence, since I/O is by several orders of magnitude slower than calculations, that means that, unless the whole data set is read into memory, algorithm II will be twice as slow, and it won't work if the data file is not seekable. --[[User:Army1987|Army1987]] 16:00, 28 October 2007 (UTC)
=== Algorithm IV ===
Doesn't the final step in West's algorithm have a typo? Instead of:
<blockquote>
Variance = S * sumweight * n / (n-1)
</blockquote>
Shouldn't it actually be:
<blockquote>
Variance = S / sumweight * n / (n-1)
</blockquote>
Looking at West's paper, he has "mathematical description" and "computational description" side by side. The math for the final line looks like:
<math>
S^2 = \frac{T}{(n-1)/n \sum w_i}
</math>
And if you work through it, <math>T</math> should be the variance times the (incremental) weight for the recurrence
to work. West's "computational description" is as its presented here, but I think its a typo in West.
[[User:Shauncutts|Shauncutts]] ([[User talk:Shauncutts|talk]]) 06:15, 29 January 2008 (UTC)
===Minor spelling and grammar fixes===
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