

\subsection{\bf Linear fits to Cross Section Data}
\subsection{\bf Example of Use of $\chi^2$---Overview}
\begin{slide}
\begin{itemize}
\item Consider the example in Mathews and Walker, page~390.
\[
\sigma (\theta) = a_0 + a_1 \cos\theta + a_2 \cos^2 \theta + a_3
\cos^3 \theta
\]

\vspace*{10pt}
\centerline{\psfig{figure=fig11.phys.ps,clip=true,width=5.5in}}
\vspace*{10pt}

\item The measurements $x_i$'s are cross sections $\sigma\left(
\theta_i \right)$ at particular scattering angles $\theta_i$, and the
theoretical predictions $\xi_i$ are linear in unknown parameters
$a_m$.

\[
\xi_i = \sum^{n_T}_{m=1} C_{im} a_m
\]
\end{itemize}
\end{slide}

