+109 Can someone please explain to me how to solve a summation with subscripts.
+33615 This just means add up the individual terms (and divide the result by n). For example
$$If the $X$'s were $X_1,X_2,X_3$ then $\sum_{k=1}^3X_k = X_1+X_2+X_3$\\\\
Sometimes you might have a function to sum, rather than a set of data; and sometimes that summation might simplify. For example\\
$$\sum_{k=1}^nk^2=\frac{n(n+1)(2n+1)}{6}$$
I should perhaps expand that last one a little:
$$$$\sum_{k=1}^nk^2=1^2+2^2+3^2+...+n^2=\frac{n(n+1)(2n+1)}{6}$$
+33615 This just means add up the individual terms (and divide the result by n). For example
$$If the $X$'s were $X_1,X_2,X_3$ then $\sum_{k=1}^3X_k = X_1+X_2+X_3$\\\\
Sometimes you might have a function to sum, rather than a set of data; and sometimes that summation might simplify. For example\\
$$\sum_{k=1}^nk^2=\frac{n(n+1)(2n+1)}{6}$$
I should perhaps expand that last one a little:
$$$$\sum_{k=1}^nk^2=1^2+2^2+3^2+...+n^2=\frac{n(n+1)(2n+1)}{6}$$
