-variables. Let @math{X_{11}, X_{12}, @dots{}, X_{1n}} denote the @math{n} observations of the
-first explanatory variable; @math{X_{21},@dots{},X_{2n}} denote the @math{n} observations of the
-second explanatory variable; @math{X_{k1},@dots{},X_{kn}} denote the @math{n} observations of the kth
+variables. Let @math{X_{11}, X_{12}}, @dots{}, @math{X_{1n}} denote the @math{n} observations of the
+first explanatory variable; @math{X_{21}},@dots{},@math{X_{2n}} denote the @math{n} observations of the
+second explanatory variable; @math{X_{k1}},@dots{},@math{X_{kn}} denote the @math{n} observations of the kth