I just completed the June $2009$ mei stats paper. On the mark scheme for question $5ii$ it shows the median being calculated using $600$, shouldn't it be $600+1$?
I thought the median was calculated using $(n+1/2)$.
Can anyone clarify this for me?
question $5ii$ link to paper: http://www.mei.org.uk/files/papers/s109ju_n3z8.pdf
There are $1200$ observations so both the value at the $600$th ordered value and at the $601$st could be taken as the median from its definition, or anything in between. Using a $\frac{n+1}{2}$ approach might suggest the average of the $600$th and the $601$st ordered values.
The mark scheme should have allowed for any of these interpretations in the interpolation so anything like $80$ or $80.125$ or $80.0625$ or rounded versions of these should have gained the mark.