J & K CET Engineering J and K - CET Engineering Solved Paper-2006

  • question_answer
    A random variable X can attain only the value 1, 2, 3, 4, 5 with respective probabilities k, 2k, 3k, 2k, k. If m is the mean of the probability  distribution, then (k, m) is equal to

    A)  \[(3,\,1/9)\]       

    B)  \[(\,1/9,3)\]

    C)  \[(\,1/8,4)\]        

    D)  \[(\,1,3)\]

    Correct Answer: B

    Solution :

    We know sum of probability distribution is 1 \[\therefore \] \[k+2k+3k+2k+k=1\] \[\Rightarrow \] \[9k=1\] \[\Rightarrow \] \[k=\frac{1}{9}\] Mean \[=\underset{i=1}{\mathop{\overset{5}{\mathop{\Sigma }}\,}}\,{{p}_{i}}{{x}_{i}}=k(1)+2k(2)+3k(3)\] \[+2k(4)+k(5)\] \[=k(1+4+9+8+5)\] \[=\frac{1}{9}\times 27=3\] \[\therefore \] \[(k,m)=\left( \frac{1}{9},3 \right)\]


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