In my study I will be measuring workload with several metrics. With heart-rate variability (HRV), electrodermal activity (EDA) and with a subjective scale (IWS). After normalization the IWS has three values:
- Workload lower than normal
- Workload is average
- Workload is higher than normal.
I want to see how well the physiological measures can predict subjective workload.
Therefore I want to use ratio data to predict ordinal values. According to: How do I run Ordinal Logistic Regression analysis in R with both numerical / categorical values? this is easily done by using the
However, I also want to account for random effects such as between-subject differences, gender, smoking etc. Looking at this tutorial, I don't see how I can add random effects to
lme4:glmer would then be an option, but this function only allows the prediction of binary data.
Is it possible to add random effects to an ordinal logistic regression?