J & K CET Engineering J and K - CET Engineering Solved Paper-2012

  • question_answer
    If mean and variance of a binomial variate X are 2 and 1 respectively, then the probability that X takes a value atleast one is

    A)  \[\frac{1}{16}\]

    B)  \[\frac{3}{16}\]

    C)  \[\frac{5}{16}\]

    D)  \[\frac{15}{16}\]

    Correct Answer: D

    Solution :

    Given mean, \[np=2\] and variance, \[npq=1\] \[\therefore \] \[2(q)\,=2\,\,\Rightarrow q=\frac{1}{2}\] \[\Rightarrow \] \[p=\frac{1}{2}\] and \[n=4\] \[\therefore \] \[P(X\ge 1)=1-P(X=0)\] \[=1{{-}^{4}}{{C}_{0}}{{\left( \frac{1}{2} \right)}^{0}}{{\left( \frac{1}{2} \right)}^{4}}\] \[=1-1\times \frac{1}{16}=\frac{15}{16}\]


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