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Statistics: Important Questions and Preparation Tips

Feb 23, 2015 14:10 IST

    Get the CBSE Class 10th Mathematics, Statistics: Important Questions & Preparation Tips. This will help with a precise description of the whole chapter along with a gist of each topic covered in the chapter. The Questions mentioned are exclusively topic oriented and are famous for its repetition in many Board papers. Consider the below mentioned points and questions at the time of preparation.

    Important Points:

           

    • When we find a grouped data instead of an ungrouped data, the very first thing is converting grouped data into class mark.


    • Assumed Mean Method: When numerical values of xi and fi becomes tedious and time consuming. In such case we will adopt assumed-mean method for calculations.


    • Step Deviation Method: Sometimes, during the application of the assumed mean method for finding the mean, the deviations di are divisible by common number h. So if we divide the values of deviation (di) by h, we would get a smaller number to multiply with fi.


    • Mode of Grouped Data: Mode is that value among the observations which occurs most often, i.e., the value of the observations having the maximum frequency. Here will discuss ways of obtaining a Mode of grouped data. The class with the maximum frequency is called the Modal Class.

    • The cumulative frequency of a class is the frequency obtained by adding the frequencies of all the classes preceding the given class.
    • The median of the grouped data is formed by:

    • Representing a cumulative frequency distribution graphically as a cumulative frequency curve, or an ogive of the less than type and of the more than type.
    • The median of grouped data can be obtained graphically as the x-coordinate of the point of intersection of the two ‘ogives’ for this data.

    Important Questions:

    • If the mean is 30 and mode is 24, then what is the median? (1 mark)
    • The runs scored by 11 players on cricket team are 45, 38, 62, 70, 7, 13, 0, 120, 41, 52, 50. Find the median score. (2 mark)
    • If median of the following observations 2, 6, 2x, 2x + 8, 20, 32 is 16, then what is the value of x? (3 mark)
    • The following table shows the mark obtained by 100 students of class X in a school during a particular academic session. Find the mode of this distribution. (3 mark)

    Marks

    No. of Students

    Less than 10

    7

    Less than 20

    21

    Less than 30

    34

    Less than 40

    46

    Less than 50

    66

    Less than 60

    77

    Less than 70

    92

    Less than 80

    100

    • Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarized as follows. Find the mean heartbeats per minute for these women, choosing a suitable method. (4 mark)

    Number of heart beats per minute

    65 – 68

    68 – 71

    71 – 74

    74 – 77

    77 – 80

    80 – 83

    83 – 86

    Number of women

    2

    4

    3

    8

    7

    4

    2

    • Draw a ‘more than type’ ogive from the following data: (4 mark)

    Weight (in gm)

    1 – 10

    11 – 20

    21 – 30

    31 – 40

    41 – 50

    51 – 60

    61 – 70

    71 – 80

    Frequency

    3

    8

    22

    14

    10

    6

    5

    2

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