JEE Main 2020 (Online) 4th September Morning ShiftQuestion 1
The mean and variance of $8$ observations are $10$ and $13.5$, respectively. If $6$ of these observations are $5,7,10,12,14,15$, then the absolute difference of the remaining two observations is :
Statistics
Solution
$\sum x=80$, known sum $=63$, so $x+y=17$. $\sum x^2=8(100+13.5)=908$, known squares $=739$, so $x^2+y^2=169$. $2xy=289-169=120\Rightarrow xy=60$; $(x-y)^2=169-120=49$, $|x-y|=7$. Option (C).