The same "distance" from EX? Is it 1/2 * EX or EX - EX ? Consider some pharmacokinetic parameter X with mean EX. (when negative values do not make sense, usually their normalĭistribution probability is neglegible small), but it is theģ. In the log-normal distribution, negative values always have Influences whose contributions multiply up is log-normallyĢ. Influences whose contributions add up is normally distributed.Ī mere reformulation is: a parameter to which there are many Speaking) the following: a parameter to which there are many The central limit theorem (of stochatics) states (informally Make the log-normality assumption a little plausible.ġ. Should state some real-world numbers *are* normally or Not even talking about the philosophical question whether we To such a question, there cannot be a unique satisfying answer. > Why are pharmacokinetic parameters log normally distributed Now let us face the difficult part of your question: Suspect "X is log-normally distributed" is another word for "log On at 11:40:06, Hans Mielke (h.de) sent the messageĭon't panic, the lognormal distribution is important and appearsįrequently, but it is not too difficult to understand.We can thenĪpply parametric tests like ANOVA and analyse it. On taking a log transformation such data can be made normal. Normal distribution is that large skewed data can be transformed andīiological data is also positively skewed- it is time Transformation of such values you will see that the distribution becomesĪlmost normal as small values change more compared to large values Normal appears normal after a log transformation.Įxample : positively skewed- ie skewed to the right. On at 15:15:36, "sulagna" (.com) sent the messageĪ log normal distribution is one in which data that doesnot appear to be.The geometric mean and CV (see the thread about statistical terms in Parameters best describing a log-normally distributed variable are Results assumes in fact a log-normal distribution for H+Ĭoncentration or sound energy, respectively. Sound energy the application of parametric statistical tests to such pH measurement for acidity is a log-transform of H+Ĭoncentration, and noise measurement in decibel is a log-transform of Tend towards a log-normal distribution, and its log-transform willįollow a normal distribution. Influenced by the multiplication/division of random influences will Values in a multiplicative rather than additive way. Pharmacokinetics, random influences (variability in enzyme activity,ĭiffusion, permeation, flow rates etc.) affect clearance and volume Similar magnitude tends to reach a normal distribution. On at 09:12:50, Thierry Buclin (.ch) sent the messageĪccording to the central limit theorem, a variable influenced by theĪddition/subtraction of a large number of random influences of.The University of Queensland, 4072 Australia (variability in expression of receptor protein complexes) to varyingĮxtents - Others may have more specific/detailed/expert explanations but It also is seen with other PK parameters and also with PD parameters Which is more "normal" looking, thus the term "log normal". Larger values more than smaller values giving rise to a distribution CL, AUC) are skewed to the right (larger values) on aįrequency plot - Taking the logs of the PK values "transforms" the Towards poor/inefficient metabolic activities, thus PK parameters which With drug metabolism, the distribution in a population is often skewed Skewed away from the symmetrical normal (non-gaussian) distribution.
"sub-populations" which is seen overall as a distribution which is Receptors) summate to a merging of a number of smaller individual
Gene arrays that code for expression of various proteins (enzymes, My (basic) understanding is that complex/overlapping This is well known and due to the complexities of variability in the
On at 19:51:49, 2.co.uk sent the message.
PharmPK Discussion List Archive - PK2005299.html - 2005 PharmPK Discussion - Log normal distribution of PK parameters PharmPK Discussion List Archive Index page