## BE parallel design [General Statistics]

Dear PKPDPKPD!

» I am a beginner PKPDPKPD and am trying to understand the procedure which is normally done by the software.

That's the best start of possible ones!

» Just few questions to your instructions:

» 1. delta: should it be a difference of the raw data and log transformed data

After you have log-transformed the data, you are only working with these (in my example the Ys and not the Xs)

» 2. why shoudl i calculate the difference not ratio

Since we are now in the log-domain, we have transformed the multiplicative model (which would call for ratios!) into an additive model (therefore we are interested in differences of logs).

May be sound confusing, but once you have applied the transformation, all the nice examples given in statistical textbooks (99% are based on differences!) are working now…

Actually you can boil it down into three steps:

» I am a beginner PKPDPKPD and am trying to understand the procedure which is normally done by the software.

That's the best start of possible ones!

**Never trust in any piece of software you haven't written yourself (and even then you should be cautious…)**

» Just few questions to your instructions:

» 1. delta: should it be a difference of the raw data and log transformed data

After you have log-transformed the data, you are only working with these (in my example the Ys and not the Xs)

» 2. why shoudl i calculate the difference not ratio

Since we are now in the log-domain, we have transformed the multiplicative model (which would call for ratios!) into an additive model (therefore we are interested in differences of logs).

May be sound confusing, but once you have applied the transformation, all the nice examples given in statistical textbooks (99% are based on differences!) are working now…

Actually you can boil it down into three steps:

- Take logs of individual data (now you have a new data set)

- Apply common statistical methods (
*t*-test, ANOVA, GLM, whatsoever,…)

- Antilog you results (point estimate, confidence limits)

—

Regards, Jaime

Regards, Jaime

### Complete thread:

- BE parallel design - pkpdpkpd, 2007-04-03 17:45 [General Statistics]
- BE parallel design - Jaime_R, 2007-04-03 18:58
- BE parallel design - pkpdpkpd, 2007-04-03 19:07
- BE parallel design - Jaime_R, 2007-04-03 19:41
- BE parallel design - pkpdpkpd, 2007-04-03 20:14
- BE parallel design - Jaime_R, 2007-04-03 20:29
- BE parallel design - pkpdpkpd, 2007-04-03 21:48
- BE parallel design - Jaime_R, 2007-04-04 15:14
- BE parallel design - Helmut, 2007-04-04 15:31
- BE parallel design - pkpdpkpd, 2007-04-04 17:32
- BE parallel design - Jaime_R, 2007-04-04 20:33

- BE parallel design - Sathya, 2008-09-01 07:21
- BE parallel design - Sathya, 2008-09-04 12:37

- BE parallel design - Helmut, 2007-04-04 15:31

- BE parallel design - Jaime_R, 2007-04-04 15:14

- BE parallel design - pkpdpkpd, 2007-04-03 21:48

- BE parallel design - Jaime_R, 2007-04-03 20:29

- BE parallel design - pkpdpkpd, 2007-04-03 20:14

- BE parallel design - Jaime_R, 2007-04-03 19:41

- BE parallel design - pkpdpkpd, 2007-04-03 19:07

- BE parallel design - Jaime_R, 2007-04-03 18:58