Question

If the mean of the data : $7,8,9,7,8,7,\lambda ,8$ is $8$, then the variance of this data is :

• A. $\frac{9}{8}$
• B. $2$
• C. $\frac{7}{8}$
• D. $1$

Answer 1

The correct option is D $1$

mean$=\frac{7+8+9+7+8+7+\lambda +8}{8}=8$
$\Rightarrow \lambda =10$
variance$=\frac{(7-8{)}^2+(8-8{)}^2+(9-8{)}^2+(7-8{)}^2+(8-8{)}^2+(7-8{)}^2+(10-8{)}^2+(8-8{)}^2}{8}$
$=1$