diff --git a/semester4/ps/ps-rb/main.pdf b/semester4/ps/ps-rb/main.pdf
index 531bdc3..35abd01 100644
Binary files a/semester4/ps/ps-rb/main.pdf and b/semester4/ps/ps-rb/main.pdf differ
diff --git a/semester4/ps/ps-rb/parts/06_stats.tex b/semester4/ps/ps-rb/parts/06_stats.tex
index 4499f2b..24aa4c7 100644
--- a/semester4/ps/ps-rb/parts/06_stats.tex
+++ b/semester4/ps/ps-rb/parts/06_stats.tex
@@ -9,3 +9,17 @@ $$
     T_l = t_l\Bigl( X_1,\ldots,X_n \Bigr)
 $$
 \smalltext{$t_l$ heisst Schätzfunktion, eine Auswertung $T_l(\omega)$ heisst Schätzwert}
+
+\definition \textbf{Erwartungstreu}
+$$
+    T \text{ Erwartungstreu } \iffdef \forall \vartheta \in \Theta:\quad \E_\vartheta\bigl[ T \bigr] = \vartheta
+$$
+
+\definition \textbf{Bias} $\quad\E_\vartheta[T] - \vartheta$
+
+\definition \textbf{MSE} $\quad\text{MSE}_\vartheta[T] = \E_\vartheta\bigl[ (T-\vartheta)^2 \bigr]$
+
+% def Schätzerfolgen / konsistent
+
+% bmk 7.7: zerlegung MSE
+