Discrete choice theory

[[this is not entirely consistent in terms of $\beta$, $\mu$, and $\beta_i$. Would probably be best to replace the $\beta$ from the dept time choice by $\mu$.]]

[[this is possibly not entirely consistent in $U_X$ and $V_X$.]]

[[It might make sense to just teach probit ... would mean however to also replace exp(...) in dept time choice by erf(...).]]