Transform Non normal data

[Axy028]

I currently working on transforming data which has  (negative and 0 ) values into normally distributed data using BOX COX transformation with PROC TRANSREG, but I am encountering an error in the log window ERROR in SAS ENTERPRISE

Ordinary missing values were found or an UNTIE transformation or the UNTIE= option was specified. The utility of the

hypothesis tests are dubious since one parameter must be estimated for each of these values. If you really want to do

this, ensure that no observations are duplicated -- combine duplicate observations and use a FREQ statement. If you do

not, the parameter count may be too large and the tests overly conservative. However, it is best to avoid this situation

altogether.

Can anyone help me resolve this issue ? Thanks Anusha

[Rick_SAS]

The Box-Cox transformation includes power transformations (with positive and negative powers) and the log transformation. Transformations such as SQRT and LOG cannot be used for data that have negative values.

An important question to ask yourself is WHY you are transforming the data. You might want to review that article "On the assumptions (and misconceptions) of linear regression" to make sure that a transformation is necessary for what you are trying to accomplish.