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Re: st: dilemma of transformation to normal dist.
on 17/05/2003 3:48 pm, Yoshiro Nagao at email@example.com wrote:
> To enable linear regression, this dependent
> was logarithm-transformed. Since a considerable number
> of records have 0 value, however, they could not be
> log-transformed. Setting an very small positive arbitrary value
> to these records would enable log-transformation.
> However, the size of this arbitrary value would
> affect the result of regression analysis.
Maybe you should think more about the meaning of your data. A lot of zeros
sounds like you may have either
- counted data: consider negative binomial regression
- data in which many values are too low to be observed: consider interval
The answer to what sort of transformation is appropriate is rarely simply
statistical. You also need to consider what is being measured, and what sort
of back-transformation will get you results on a scale that makes sense to
the people who are interpreting the findings.
Ronan M Conroy (firstname.lastname@example.org)
Lecturer in Biostatistics
Royal College of Surgeons
Dublin 2, Ireland
+353 1 402 2431 (fax 2764)
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