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10th Class Mathematics Statistics Question Bank Statistics

  • question_answer
    A class teacher has the following absentee record of 40 students of a class for the whole term. Find the mean number of days a student was absent. (NCERT question, slightly modified)
    Number of days Number of students
    0 - 5 11
    5 - 10 10
    10 - 15 7
    15 - 20 4
    20 - 25 4
    25 - 30 3
    30 - 35 1
     

    A)  11.625

    B)  10.375

    C)  8.965              

    D)  12.25

    Correct Answer: A

    Solution :

    (a):
      \[{{x}_{i}}\] \[{{f}_{i}}\] \[{{f}_{i}}{{x}_{i}}\]
    0 ? 5 2.5 11 27.5
    5 ? 10 7.5 10 75.0
    10 ? 15 12.5 7 87.5
    15 ? 20 17.5 4 70.0
    20 ? 25 22.5 4 90.0
    25 ? 30 27.5 3 82.5
    30 ? 35 32.5 1 32.5
    \[\sum{{{f}_{i}}{{x}_{i}}=465}\] \[\therefore \overline{x}=\frac{\sum{{{f}_{i}}{{x}_{i}}}}{\sum{{{f}_{i}}}}=\frac{465}{40}=11.625\]                


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