A) 2
B) 4
C) 22
D) 11
E) 44
Correct Answer: C
Solution :
Here,\[n=7,\]sum =315 Now, Mean\[=\frac{315}{7}=45\] \[\therefore \]Standard deviation \[=\sqrt{\frac{\begin{align} & {{(12-45)}^{2}}+{{(23-45)}^{2}}+{{(34-45)}^{2}} \\ & +{{(45-45)}^{2}}+{{(56-45)}^{2}}+{{(67-45)}^{2}} \\ & +{{(78-45)}^{2}} \\ \end{align}}{7}}\] \[=\sqrt{\frac{\begin{align} & {{(33)}^{2}}+{{(22)}^{2}}+{{(11)}^{2}}+0 \\ & +{{(11)}^{2}}+{{(22)}^{2}}+{{(33)}^{2}} \\ \end{align}}{7}}\] \[=\sqrt{\frac{2(1089+484+121)}{7}}=\sqrt{\frac{3388}{7}}\] \[=\sqrt{484}=22\]
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