[Turing-Southampton] S3RI seminar: Carolin Jenkner, Thursday 2-3pm

[Helen Ogden]

Dear all,

On Thursday (1 November) at 2pm in 54 / 7035 (7B), we have an S3RI 
seminar from Carolin Jenkner, University of Freiburg on "Multivariable 
modeling of continuous covariates with a spike at zero". Details are 
given below.

The seminar will also be available via a live web-cast at
https://coursecast.soton.ac.uk/Panopto/Pages/Viewer.aspx?id=c2bc1d87-ef9e-46a3-91a1-912ed9a8704e

The talk will be followed by tea and cake in the staff reading room on 
level 4 of building 54.

All are welcome!

Best wishes,

Helen

Multivariable modeling of continuous covariates with a spike at zero

Carolin Jenkner, University of Freiburg

In a lot of clinical and epidemiological studies, covariates with a 
large amount of observations with value zero occur. One simple example 
is the covariate "cigarettes smoked per day''. Here non-smokers take 
value zero, so that in studies investigating the effect of this 
covariate the amount of zeros will be relatively high. Covariates with a 
spike at zero (SAZ) are continuous covariates with this special 
distribution. The proportion of observations with value zero is higher 
than for continuous covariates with standard distributions (e.g. normal 
distribution etc.). In this talk the properties of these covariates as 
predictor variables in statistical models is investigated and how their 
effect on different outcomes can be modelled appropriately. For 
analysing the effect of two covariates with SAZ on an outcome variable, 
four modelling strategies including different binary indicator 
covariates are proposed. All four methods are extensions of a non-linear 
modelling technique for one covariate with SAZ based on fractional 
polynomials (FPs) with inclusion of a binary variable indicating if the 
covariate is zero or not (FP-spike). Results of a simulation study, in 
which the four methods are investigated and compared to standard linear 
regression and FP as non-linear modelling technique will be presented. 
For illustration, application to data of a study on laryngeal cancer is 
presented.


For the current schedule of S3RI seminars, see 
https://tinyurl.com/s3riseminar

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