+0

# Can someone please explain to me how to solve a summation with subscripts.

0
889
3
+109

Can someone please explain to me how to solve a summation with subscripts.

May 21, 2014

#3
+33615
+10

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}$$I should perhaps expand that last one a little:$$$$\sum_{k=1}^nk^2=1^2+2^2+3^2+...+n^2=\frac{n(n+1)(2n+1)}{6}$$

May 22, 2014

#1
+128408
+5

Could you provide an example of what you want to do??

May 21, 2014
#2
+109
0

Let's take the Law of Large Numbers for instance:

May 21, 2014
#3
+33615
+10
$$If the X's were X_1,X_2,X_3 then \sum_{k=1}^3X_k = X_1+X_2+X_3\\\\ Sometimes you might have a function to sum, rather than a set of data; and sometimes that summation might simplify. For example\\$$\sum_{k=1}^nk^2=\frac{n(n+1)(2n+1)}{6}$$I should perhaps expand that last one a little:$$$$\sum_{k=1}^nk^2=1^2+2^2+3^2+...+n^2=\frac{n(n+1)(2n+1)}{6}$$