Suppose that the vectors \(\left( {{X_1},{Y_1}} \right),\left( {{X_2},{Y_2}} \right),...,\left( {{X_n},{Y_n}} \right)\) form a random sample of two-dimensional vectors from a bivariate normal distribution for which the means, the variances, and the correlation are unknown. Show that the following five statistics are jointly sufficient:
\(\sum\limits_{i = 1}^n {{X_i}} ,\sum\limits_{i = 1}^n {{Y_i}} ,\sum\limits_{i = 1}^n {X_i^2} ,\sum\limits_{i = 1}^n {Y_i^2} \,\,\,\,{\rm{and}}\,\,\,\,\sum\limits_{i = 1}^n {{X_i}{Y_i}} \)