A) 4
B) 6
C) 8
D) 2
Correct Answer: D
Solution :
Let 5th observation be \[x.\] Given mean =7 \[\therefore \] \[7=\frac{6+7+8+10+x}{5}\] \[\Rightarrow \]\[x=4\] Now, Variance \[=\sqrt{\frac{{{(6-7)}^{2}}+{{(7-7)}^{2}}+{{(8-7)}^{2}}+{{(10-7)}^{2}}+{{(4-7)}^{2}}}{5}}\]\[=\sqrt{\frac{{{1}^{2}}+{{0}^{2}}+{{1}^{2}}+{{3}^{2}}+{{3}^{2}}}{5}}=\sqrt{\frac{20}{5}}=\sqrt{4}=2\]
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