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Chapter 4 - The Modelling of Time

Published online by Cambridge University Press:  20 April 2023

Jos W. R. Twisk
Affiliation:
Amsterdam University Medical Centers
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Summary

In Chapter 4, the modelling of the time variable in longitudinal data analysis is discussed. In general, a distinction can be made between time as a continuous variable and time as a categorical variable represented by dummy variables. The latter is only possible in a longitudinal study with fixed time-points. Basically, three different situations are explained. (1) Growth curve analysis; i.e. when the time variable is the covariate of interest. Regarding growth curve analysis, the chapter also includes a discussion about latent class growth curve modelling. (2) The time variable as a potential confounder. When the time variable is a potential confounder it is argued that it is important to distinguish the time variable from age and (3) the time variable as effect modifier. When the time variable is an effect modifier, the interest is either in a different development over time for different groups or in a different relationship between an outcome variable and a covariate in different parts of the longitudinal study. Both situations are discussed in detail. All methods are accompanied by extensive real-life data examples.

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Publisher: Cambridge University Press
Print publication year: 2023

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  • The Modelling of Time
  • Jos W. R. Twisk, Amsterdam University Medical Centers
  • Book: Applied Longitudinal Data Analysis for Medical Science
  • Online publication: 20 April 2023
  • Chapter DOI: https://doi.org/10.1017/9781009288002.005
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  • The Modelling of Time
  • Jos W. R. Twisk, Amsterdam University Medical Centers
  • Book: Applied Longitudinal Data Analysis for Medical Science
  • Online publication: 20 April 2023
  • Chapter DOI: https://doi.org/10.1017/9781009288002.005
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • The Modelling of Time
  • Jos W. R. Twisk, Amsterdam University Medical Centers
  • Book: Applied Longitudinal Data Analysis for Medical Science
  • Online publication: 20 April 2023
  • Chapter DOI: https://doi.org/10.1017/9781009288002.005
Available formats
×