Class 9 – Statistics – Important Questions

Important Questions

Statistics – Important Questions

  1. Mean of 20 observations is 17. If in the observations, observation 40 is replaced by 12, find the new mean
  2. What is the mean of first 10 natural numbers?
  3. The mean of 100 observations is 50. If one of the observation which was 50 is replaced by 150 then what will be the resulting mean?
  4. The number of family members in 10 flats of a society are
    2, 4, 3, 3, 1, 0, 2, 4, 1, 5.
    Find the mean number of family members per flat.
  5. If the mean of 6, 8, 9, x, 13 is, find the value of x,
  6. A cricketer has a mean score of 58 runs in nine innings. Find out how many runs are to be scored by him in the tenth innings to raise the mean score to 61.
  7. The mean weight of a class of 34 students is 46.5 kg. If the weight of the new boy is included, the mean is rises by 500 g. Find the weight of the new boy.
  8. The weight (in kg) of 7 students of a class are 44, 52, 55, 60, 50, 49, 45. Find the median weight.
  9. The width of each of five continuous classes in a frequency distribution is 5 and the lower class limit of the lowest class is 10. What is the upper class limit of the highest class?
  10. The following data given the weight (in grams) of 30 oranges picked from a basket:
    106 107 76 109 187 95 125 92 70
    139 128 100 88 84 99 113 204 141
    136 123 90 115 110 97 90 107 75
    80 118 82
    Construct a grouped frequency distribution table taking class width equal to 20 in such a way that the mid-value of first class in 70. From the frequency table, find the number of oranges
    1. weighing more than 180 g.
    2. less than 100 g.
  11. The blood groups of 30 students of Class VIII are recorded as follows:
    A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O,
    A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O.
  12. Given below are the seats won by different political parties in the polling outcome of a state assembly elections:
Political partyABCDEF
Seats won 755537291037

(i) Draw a bar graph to represent the polling results.
(ii) Which political party won the maximum number of seats?

13. A teacher wanted to analyse the performance of two sections of students in a mathematics test of 100 marks. Looking at their performances, she found that a few students got under 20 marks and a few got 70 marks or above. So she decided to group them into intervals of varying sizes as follows: 0 – 20, 20 – 30, . . ., 60 – 70, 70 – 100. Then she formed the following table:

MarksNumber of students
0 – 20 7
20 – 3010
30 – 4010
40 – 5020
50 – 6020
60 – 7015
70 – above8
Total90

Draw a histogram to represent the given data.

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