some textual improvements of assignments

projects/project_onset_fi/onset_fi.tex

@@ -37,7 +37,8 @@ of the stimulus \textbf{I}ntensity.
 
 \begin{questions}
   \question In the accompanying datasets you find the
-  \textit{spike\_times} of an P-unit electrorecptor to a stimulus of a
+  \textit{spike\_times} of an P-unit electrorecptor of the weakly
+  electric fish \textit{Apteronotus leptorhynchus} to a stimulus of a
   certain intensity, i.e. the \textit{contrast}. The contrast is also
   part of the file name itself.
   \begin{parts}
@@ -57,6 +58,7 @@ of the stimulus \textbf{I}ntensity.
     where $\alpha$ is the starting firing rate, $\beta$ the saturation
     firing rate, $x$ the current stimulus intensity, $x_0$ starting
     stimulus intensity, and $dx$ a measure of the slope.
+    \part Plot the fit into the data.
   \end{parts}
 \end{questions}