At 12:52 PM 12/14/99 -0800, Dale Berger wrote:
>Just a reminder that transformations can be used on proportions as a dv to
reduce
>the skew, important if some values approach 0 or 1. These include arcsine,
>probit, and logit. Each needs special treatment when p=0 or p=1. Cohen
and Cohen
>(2nd ed. of Applied MR/C) has a section on transformations for proportions
(pp.
>265-270).
I'll just add the usual caveat that hasn't yet been mentioned in these
responses about proportions: the transformations, use of the binomial, and
comment about proportions just being means all assume that the data really
are proportions, not ratios -- that is, that the denominator is fixed among
all values, not variable. The problem is that many people use the terms
interchangably, talking about proportions or percentages when they're
actually dealing with ratios.
Rich Strauss
========================
Dr Richard E Strauss
Biological Sciences
Texas Tech University
Lubbock TX 79409-3131
Email: [EMAIL PROTECTED]
Phone: 806-742-2719
Fax: 806-742-2963
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