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exercises/schizo.md

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