61 lines
1.9 KiB
Markdown
61 lines
1.9 KiB
Markdown
Exercise: Growth curve model with interaction
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## Risperidone vs. haloperidol and schizophrenia (Möller et al. 2008)
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Analyze the data from [moeller.csv](../data/moeller.csv):
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- `pans`: Positive and Negative Symptom Scale for schizophrenia
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- `treat`: medication group
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- `risp`: atypical neuroleptic risperidone
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- `halo`: conventional neuroleptic haloperidol
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``` r
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dat <- read.table("../data/moeller.csv", header = TRUE, sep = ",")
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dat$id <- factor(dat$id)
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dat$treat <- factor(dat$treat, levels = c("risp", "halo"))
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lattice::xyplot(pans ~ week, data = dat, groups = treat,
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type = c("g", "p", "a"), auto.key = TRUE)
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```
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<img src="schizo_files/figure-gfm/unnamed-chunk-2-1.png" alt="" style="display: block; margin: auto;" />
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- What is the sample size in each treatment group?
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- Estimate a random slope model
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- What are the estimates for the fixed effects and variance
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components?
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- Fit a model with quadratic time trends for the population and
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individual subjects
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- Add an interaction with treatment for the linear and the quadratic
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effects for week and test them
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- Interpret your results: Which model would you choose?
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- Refit the model that you chose with a centered week variable:
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- Compare the estimates for your fixed effects and the covariance
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components
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- Which estimates change and why?
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### Reference
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<div id="refs" class="references csl-bib-body hanging-indent">
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<div id="ref-Moeller08" class="csl-entry">
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Möller, H.-J., M. Riedel, M. Jäger, F. Wickelmaier, W. Maier, K.-U.
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Kühn, G. Buchkremer, et al. 2008. “Short-Term Treatment with Risperidone
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or Haloperidol in First-Episode Schizophrenia: 8-Week Results of a
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Randomized Controlled Trial Within the German Research Network on
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Schizophrenia.” *International Journal of Neuropsychopharmacology* 11
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(7): 985–97. <https://doi.org/10.1017/S1461145708008791>.
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</div>
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</div>
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