Rich Strauss <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]...
> However, the arcsin transformation is for proportions (with fixed
It's also designed for stabilising variance rather than specifically inducing
symmetry.
Does it actually produce symmetry as well?
> denominator), not for ratios (with variable denominator). The "proportion
> of sentences in a number of texts that belong to a certain category" sounds
> like a problem in ratios, since the total number of sentences undoubtedly
> vary among texts. Log transformations work well because they linearize
> such ratios.
Additionally for small proportions logs are close to logits, so logs are
sometimes
helpful even if the data really are proportions. Logs also go some way to
reducing
the skewness and stabilising the variance, though they don't stabilise it as
well
as the arcsin square root that's specifically designed for it.
Glen
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