
15.5.5 Two-dimensional random variables and their characteristics
Problem:
The discrete random variables \( \xi_{1} \) and \( \xi_{2} \) are independent and have the following distribution tables:
\( \xi_{1} \)
\begin{tabular}{|c|c|c|c|}
\hline\( x_{i} \) & 0 & 1 & 3 \\
\hline\( p_{i} \) & \( 1 / 2 \) & \( 3 / 2 \) & \( 1 / 8 \) \\
\hline
\end{tabular}
\[
\xi_{2}
\]
\begin{tabular}{|c|c|c|}
\hline\( y_{j} \) & 0 & 1 \\
\hline\( q_{j} \) & \( 1 / 3 \) & \( 2 / 3 \) \\
\hline
\end{tabular}
1) Find the distribution table of the random vector \( \eta=\left(\xi_{1}, \xi_{2}\right)^{T} \), composed of these variables.
2) Calculate the expected value and the dispersion of each random variable.
3) Calculate the correlation moment \( V_{\xi_{1} \xi_{2}} \), and then find \( E\left[\xi_{1}, \xi_{2}\right] \). Will these variables be correlated? Would it be possible, without calculating \( V_{\xi_{1} \xi_{2}} \), to immediately assume what it is equal to?