JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2011

  • question_answer
        If the algebraic sum of deviations of 20 observations from 30 is 20, then the mean of observations is

    A)  30                                         

    B)  30.1

    C)  29                                         

    D)  31

    Correct Answer: D

    Solution :

                    Given, \[\sum\limits_{i=1}^{20}{({{x}_{i}}-30)=20}\] \[\Rightarrow \]               \[\sum\limits_{i=1}^{20}{{{x}_{i}}-20\times 30=20}\] \[\Rightarrow \]               \[\sum\limits_{i=1}^{20}{{{x}_{i}}}=620\] \[\therefore \]  Mean\[=\frac{\sum\limits_{i=1}^{20}{{{x}_{i}}}}{20}=\frac{620}{20}=31\]


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