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Q. If the data $x_1, x_2, ...., x_{10}$ 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 :

JEE MainJEE Main 2019Statistics

Solution:

$x_{1} + .... +x_{4} =44 $
$ x_{5} + .... + x_{10} = 96 $
$ \bar{x} = 14, \sum x_{i} = 140 $
Variance $ = \frac{\sum x_{1}^{2}}{n} - \bar{x}^{2} = 4 $
Standard deviation = $2$