Submitted by kingcrepe on Tue, 03/27/2018 - 19:21
Forums:
Hopefully someone will be able to clarify something small on STEP 3 Q1 2010. On every worked solution I've seen (e.g MEI step solutions/TSR solutions), when completing part (ii) the A^2 term isn't multiplied by 1/n . I understand why the summation does not remain, but surely a^2 will be multiplied by 1/n? Also in the notation for (ii), is the A^2 supposed to be with the (Xk)^2 and multiplied by 1/n, or not? Thank you in advance!
Sums
$A^2$ is a number. If we find $\sum_{i=1}^n A^2$ this will be $A^2+A^2+ ... +A^2 = nA^2$. Hence
$\frac 1 n \sum_{i=1}^n A^2 = \frac 1 n \times nA^2 = A^2$.
Hope this helps!
Thank you!
Thank you!