JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    The mean of a set of observations is\[x\]. If each observation is divided by \[\alpha ,\,\,\alpha \ne 0\] and then is increased by\[10\], then the mean of the new set is

    A) \[\frac{{\bar{x}}}{\alpha }\]                                        

    B) \[\frac{\bar{x}+10}{\alpha }\]

    C)  \[\frac{\bar{x}+10\alpha }{\alpha }\]                     

    D)  \[\alpha \bar{x}+10\]

    Correct Answer: C

    Solution :

    Let\[{{x}_{1}},\,\,{{x}_{2}},\,\,...,\,\,{{x}_{n}}\]be \[n\] observations. Then,    \[\bar{x}=\frac{1}{n}\Sigma {{x}_{i}}\] let           \[{{y}_{i}}=\frac{{{x}_{i}}}{\alpha }+10\] Then,    \[\frac{1}{n}\sum\limits_{i=1}^{n}{\frac{1}{\alpha }}\left( \frac{1}{n}\Sigma {{x}_{i}} \right)+\frac{1}{n}(10n)\] \[\Rightarrow \]               \[\bar{y}=\frac{1}{\alpha }\bar{x}+10\] \[\Rightarrow \]               \[\bar{y}=\frac{\bar{x}+10\alpha }{\alpha }\]


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