BCECE Engineering BCECE Engineering Solved Paper-2004

  • question_answer
    If the two lines of regression are\[x+4y=3\]and \[3x+y=5,\]then value of \[x\] for \[y=3\]is:      

    A)  \[\frac{2}{3}\]                  

    B)         \[-9\]                   

    C)  \[~-4\]                

    D)         none of these     

    Correct Answer: A

    Solution :

    Let us assume line of regression y on X is \[x+4y=3\]or \[4y=-x+3\]             ?(i) and X on Y is \[3x+y=5\] or\[~3x=-\text{ }y+5\] ...(ii)                 \[\Rightarrow \]               \[{{b}_{YX}}=-\frac{1}{4}\]and \[{{b}_{XY}}=-\frac{1}{3}\]                 Now, \[r=-\sqrt{\left( -\frac{1}{4} \right)\left( -\frac{1}{3} \right)}=-\frac{1}{\sqrt{12}}>-1\]                 \[\therefore \] Our assumption is true. Since, \[y=3\]is given, we have to find the value of \[x,\] now we take Eq. (ii)                                 \[3x=-3+5\Rightarrow x=\frac{2}{3}\] Note: If two regression lines are given, then we assume any of y on x and x on y. If the square root of the product of regression coefficient lies between\[-1\]to 1, then the our assumption is true, otherwise it is opposite.


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