When to do transformation of data?

From: "atul" Subject: [NMusers] When to do transformation of data? Date: Tue, April 23, 2002 2:27 am Hello All Is there any reference paper which discusses the various methods for transformation of data and its implication in NONMEM analysis? Could the group share their experience on data transformations? Especially what aspects of nontransformed data should be looked into before selecting the suitable transformation of data. In one of the analysis I was observing that log transformation of data helps in getting better estimates and the analysis is more stable. The data is after infusion studies in patients who are also on several concomitant medications. However, I was able to fit the data of healthy subjects data with out any transformation. What could be the possible reasons for these type of observations? Thanks in advance for your time Venkatesh Atul Bhattaram Post-doctoral Fellow University of Florida Gainesville