Statistics Test...

For the observations $${ x }_{ 1, }{ x }_{ 2 },{ x }_{ 3 },........{ x }_{ 18, }$$ it is given that $$\sum _{i =1 }^{ 18 }{ ({ x }_{ i }-8)=9 } $$ and $$\sum _{  j=1}^{ 18 }{ { ({ x }_{ j}-8) }^{ 2 }=45 } $$ then the standard deviation of these eighteen observations is 

the coefficient of quartile deviation is 

Mode of the data $$3,2,3,2,3,5,6,6,5,3,2,5$$ is

The variance of the elements of the row which contains  $$2019$$  is  $$K$$  then the value of  $$3 K$$  is

The variance of first $$30$$ natural numbers, is

If the mean deviation about the median of the numbers $$a,2a,....,50a$$ is $$50$$, then $$|a|$$ equals:-

The variance of first $$50$$ even natural numbers is:-

Two distributions each of $$5$$ observations having veriance $$4$$ and $$5$$. If their arithmetic mean are $$2$$ and $$4$$ respectively., Find the variance of combined distribution 

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If $$\displaystyle\sum _{ i=1 }^{ 18 }{ \left( { x }_{ i }-8 \right)  } =153,\displaystyle\sum _{ i=1 }^{ 18 }{ \left( { x }_{ i }-8 \right) ^{ 2 } } =45$$ then standard deviation of $$x_{1},x_{2},........,x_{n}$$ is