PK/PD Modeling & Simulation

What is the -2LL or the Log-likelihood Ratio?

Nathan Teuscher

If you have ever read the literature on pharmacokinetic modeling and simulation, you are likely to have run across the phrase  “-2LL” or “log-likelihood ratio”. These are statistical terms that are used when comparing two possible models. In this post, I hope to explain with the log-likelihood ratio is, how to use it, and what […]

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Topics: PK/PD Modeling & Simulation

Using Sampling “Windows” for PK Blood Samples

Nathan Teuscher

One of the most common questions posed by clinical operations experts when including pharmacokinetic sampling in a clinical trial is the following: “What is the time window we should allow for each blood sample?” My answer is always the same: “Don’t include any window.” I am almost always met with a confused look. The confusion is […]

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Topics: PK/PD Modeling & Simulation

What is “Adjusted” r-squared?

Nathan Teuscher

Linear regression is a common tool that the pharmacokineticist uses to calculate elimination rate constants. Standard linear regression provides estimates for the slope, intercept, and r2, a statistic that helps define goodness of fit. Statistical texts define r2 as the coefficient of determination and it is calculated using the following equation: where SS = the sum of […]

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Topics: PK/PD Modeling & Simulation

Demystifying CDISC, SDTM, and ADaM

Nathan Teuscher

Team discussions regarding CDISC often bring in the mists of darkness, which obscure the landscape and prevent us from moving in a clear direction. Then if we weren’t confused enough, the discussion moves to SDTM, ADaM, and clinical databases, and we feel like we are spinning out of control. The land of clinical study data can […]

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Topics: PK/PD Modeling & Simulation
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