2. Solved Papers
  3. JEE Main & Advanced

JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
                                     In a set of 2n observations, half of them ear equal to \['a'\] and the remaining half are equal to \['-a'\] If the standard deviation of all the observations is 2; then the value of \[\left| a \right|\]is :     JEE Main Online Paper ( Held On 25  April 2013 )

    A)                 2             

    B)                                        \[\sqrt{2}\]

    C)                                        4                                             

    D)                                        \[2\sqrt{2}\]

    Correct Answer: A

    Solution :

                    Clearly mean A =0                             Now, standard deviation \[\sigma =\sqrt{\frac{\Sigma {{(x-A)}^{2}}}{2n}}\] \[2=\sqrt{\frac{{{(a-0)}^{2}}+{{(a-0)}^{2}}+.....+{{(0-a)}^{2}}+.......}{2n}}\] \[=\sqrt{\frac{{{a}^{2}}.2n}{2n}}=|a|\]Hence,\[|a|=2\]


You need to login to perform this action.
You will be redirected in 3 sec spinner