Class 7 Maths Chapter 3 Data Handling Exercise 3.2 pdf notes:-
Exercise 3.2 Class 7 maths Chapter 3 Pdf Notes:-
Ncert Solution for Class 7 Maths Chapter 3 Data Handling Exercise 3.2 Tips:-
The most common representative value of a group of data is the arithmetic mean or the
mean. To understand this in a better way, let us look at the following example:
Two vessels contain 20 litres and 60 litres of milk respectively. What is the amount that
each vessel would have, if both share the milk equally? When we ask this question we are
seeking the arithmetic mean.
As we have said Mean is not the only measure of central tendency or the only form of
representative value. For different requirements from a data, other measures of central
tendencies are used.
Look at the following example
To find out the weekly demand for different sizes of shirt, a shopkeeper kept records of sales
of sizes 90 cm, 95 cm, 100 cm, 105 cm, 110 cm. Following is the record for a week:
Size (in inches) 90 cm 95 cm 100 cm 105 cm 110 cm Total
Number of Shirts Sold 8 22 32 37 6 105
If he found the mean number of shirts sold, do you think that he would be able to
decide which shirt sizes to keep in stock?
Mean of total shirts sold =
Total number of shirts sold
Number of different sizes of shirts = = 105
Should he obtain 21 shirts of each size? If he does so, will he be able to cater to the
needs of the customers?
The shopkeeper, on looking at the record, decides to procure shirts of sizes 95 cm,
100 cm, 105 cm. He decided to postpone the procurement of the shirts of other sizes
because of their small number of buyers.
Look at another example
The owner of a readymade dress shop says, “The most popular size of dress I sell is the
size 90 cm.
Observe that here also, the owner is concerned about the number
of shirts of different sizes sold. She is however looking at the shirt size
that is sold the most. This is another representative value for the data.
The highest occuring event is the sale of size 90 cm.This representative
value is called the mode of the data.
The mode of a set of observations is the observation that occurs
EXAMPLE 4 Find the mode of the given set of numbers: 1, 1, 2, 4, 3, 2, 1, 2, 2, 4
SOLUTION Arranging the numbers with same values together, we get
1, 1, 1, 2, 2, 2, 2, 3, 4, 4
Mode of this data is 2 because it occurs more frequently than other observations.
3.6.1 Mode of Large Data
Putting the same observations together and counting them is not easy if the number of
observations is large. In such cases we tabulate the data. Tabulation can begin by putting
tally marks and finding the frequency, as you did in your previous class.