These NCERT Solutions for Class 9 Maths Chapter 14 Statistics Ex 14.2 Questions and Answers are prepared by our highly skilled subject experts.
NCERT Solutions for Class 9 Maths Chapter 14 Statistics Exercise 14.2
Question 1.
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.
Represent this data in the form of a frequency distribution table. Which is the most common and which is the rarest blood group among these students.
Solution:
The frequency distribution table of the following data is as:
The most common blood group is O, and the rarest blood group is AB among the students.
Question 2.
The distance (in km) of 40 female engineers from their residence to their place of work was found as follows:
Construct a grouped frequency distribution table with class size 5 for the data given above, taking the first interval as 0-5 (5 not included). What main features do you observe from this tabular representation?
Solution:
Upper limit = 32
Lower limit = 2
Range = 32 – 2 = 30
We observe that more than 60% of female engineers’ residence to their place of work were less than 15 km.
Question 3.
The relative humidity (in %) of a certain city for a month of 30 days was as follows:
(i) Construct a grouped frequency distribution table with classes 84 – 86, 86 – 88 etc.
(ii) Which month or season do you think this data is about?
(iii) What is the range of this data?
Solution:
(i) Upper limit = 99.2
Lower limit = 84.9
Range = 14.3
(ii)The given data is to be taken in the rainy season as the relative humidity is high.
(iii) The range of this data is 99.2 – 84.9 = 14.3
Question 4.
The height of 50 students, measured to the nearest centimeter have been found to be as follows:
(i) Represent the data given above by a grouped frequency distribution table, taking the class intervals as 160 – 165, 165 – 170, etc.
(ii) What can you conclude about their height from the above table.
Solution:
(i) Upper limit = 173
Lower limit = 150
Range = 173 – 150 = 23
(ii) One conclusion that we can draw from the above table is that more than 50% of students are shorter than 165 cm.
Question 5.
A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city, The data obtained for 30 days is as follows:
(i) Make a grouped frequency distribution table for this data with class intervals as 0.00 – 0.04, 0.04 – 0.08, and so on.
(ii) For how many days, was the concentration of sulphur dioxide more than 0.11 parts per million?
Solution:
(i) Upper limit = 0.22
Lower limit = 0.01
Range = 0.21
(ii) The concentration of sulphur dioxide was more than 0.11 ppm for 8 days.
Question 6.
Three coins were tossed 30 times simultaneously. Each time the number of heads occurring was noted down as follows:
Prepare a frequency distribution table for the data given above.
Solution:
The frequency distribution table of the given data is
Question 7.
The value of π upto 50 decimal places is given below:
3.14159265358979323846264338327950288419716939937510
(i) Make a frequency distribution of the digits from 0 to 9 after the decimal point.
(ii) What are the most and the least frequently occurring digits?
Solution:
(i) Frequency distribution table of the digits after the decimal point is:
(ii) The most frequently occurring digits are 3 and 9. The least occurring digits are 0.
Question 8.
Thirty children were asked about the number of hours they watched TV programmes in the previous week. The results were found as follows:
(i) Make a grouped frequency distribution table for this data, taking class width 5 and one of the class intervals as 5 – 10.
(ii) How many children watched television for 15 or more hours a week?
Solution:
Upper limit = 17
Lower limit = 1
Range = 17 – 1 = 16
(ii) Number of children who watched television for 15 or more hours a week is 2 children.
Question 9.
A Company manufactures car batteries of a particular type. The lives (in years) of 40 such batteries were recorded as follows:
Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the interval 2 – 2.5:
Solution:
Upper limit = 4.6
Lower limit = 2.2
Range = 2.4
