JEE Main & Advanced Mathematics Statistics Question Bank Self Evaluation Test - Statistics

  • question_answer
    The average of n numbers \[{{x}_{1}},{{x}_{2}},{{x}_{3}},...{{x}_{n}}\] is M. If \[{{x}_{n}}\] is replaced by \[x',\] then new average is

    A) \[M-{{x}_{n}}+x'\]

    B) \[\frac{nM-{{x}_{n}}+x'}{n}\]

    C) \[\frac{(n-1)M+x'}{n}\]

    D) \[\frac{M-{{x}_{n}}+x'}{n}\]

    Correct Answer: B

    Solution :

    [b] \[M=\frac{{{x}_{1}}+{{x}_{2}}+{{x}_{3}}...{{x}_{n}}}{n}\] \[nM={{x}_{1}}+{{x}_{2}}+{{x}_{3}}+...+{{x}_{n-1}}+{{x}_{n}}\] i.e., \[nM-{{x}_{n}}={{x}_{1}}+{{x}_{2}}+{{x}_{3}}+...+{{x}_{n-1}}\] \[\frac{nM-{{x}_{n}}+x'}{n}=\frac{{{x}_{1}}+{{x}_{2}}+{{x}_{3}}+...{{x}_{n-1}}+x'}{n}\] \[\therefore \] New average \[=\frac{nM-{{x}_{n}}+x'}{n}\]


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