BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    Lines of regressions of \[y\] on \[x\] and \[x\] on \[y\] are respectively \[y=ax+b\]and\[x=\alpha y+\beta ,\] If mean of \[x\]and\[y\] series is same, then its value. is

    A)  \[\frac{b}{1-a}\]                  

    B)         \[\frac{1-a}{b}\]                  

    C)         \[\frac{\beta }{1-\beta }\]                 

    D)         \[\frac{a}{1-\alpha }\]

    Correct Answer: A

    Solution :

    Let mean of \[x\]and \[y\]series are \[\bar{x}\]and\[\bar{y}.\] Lines of regression pass through mean \[(\bar{x},\bar{y}).\] \[\therefore \]      \[\bar{y}=a\bar{x}+b,\bar{x}=\alpha \bar{y}+\beta \] Given that,             \[\bar{x}=\bar{y}\]                 \[\therefore \]      \[\bar{x}=a\bar{x}+b,\bar{x}=\alpha \bar{x}+\beta \]                 \[\Rightarrow \]    \[\bar{x}=\frac{b}{1-a},\bar{x}=\frac{\beta }{1-\alpha }\]


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