13.Statistics
normal

જો $x_1,x_2,.........,x_{100}$ એ $100$ અવલોકનો એવા છે કે જેથી $\sum {{x_i} = 0,\,\sum\limits_{1 \leqslant i \leqslant j \leqslant 100} {\left| {{x_i}{x_j}} \right|} }  = 80000\,\& $ મધ્યકથી સરેરાશ વિચલન $5$ હોય તો પ્રમાણિત વિચલન મેળવો. 

A

$10$

B

$30$

C

$40$

D

$50$

Solution

$\bar{x}=\frac{\sum x_{i}}{100}=0$  and 

$\frac{\sum\left|x_{i}-\bar{x}\right|}{100}=5 \Rightarrow \sum\left|x_{i}\right|=500$

$ \Rightarrow \sum {x_i^2}  + 2\sum\limits_{1 \le i < j \le 100} {\left| {{x_i}{x_j}} \right|}  = {(500)^2}$

$\Rightarrow \frac{\sum x_{i}^{2}}{100}=\frac{(500)^{2}-2 \sum\left|x_{i} x_{j}\right|}{100}=2500-1600$

$S. D.=\sqrt{\frac{\sum\left(x_{i}-\bar{x}\right)^{2}}{100}}=\sqrt{900}=30$

Standard 11
Mathematics

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