Question:
If the data $\mathrm{x}_{1}, \mathrm{x}_{2}, \ldots . \mathrm{x}_{10}$ is such that the mean of first four of these is 11 , the mean of the remaining six is 16 and the sum of squares of all of these is 2,000 ; then the standard deviation of this data is :
Correct Option: , 2
Solution:
$\mathrm{x}_{1}+\ldots+\mathrm{x}_{4}=44$
$\mathrm{x}_{5}+\ldots+\mathrm{x}_{10}=96$
$\overline{\mathrm{x}}=14, \Sigma \mathrm{x}_{\mathrm{i}}=140$
Variance $=\frac{\sum \mathrm{x}_{\mathrm{i}}^{2}}{\mathrm{n}}-\overline{\mathrm{x}}^{2}=4$
Standard deviation $=2$