Class 7 Maths Chapter 3 Data Handling Exercise 3.3 pdf notes:-
Exercise 3.3 Class 7 maths Chapter 3 Pdf Notes:-
Ncert Solution for Class 7 Maths Chapter 3 Data Handling Exercise 3.3 Tips:-
USE OF BAR GRAPHS WITH A DIFFERENT PURPOSE
We have seen last year how information collected could be first arranged in a frequency
distribution table and then this information could be put as a visual representation in the
form of pictographs or bar graphs. You can look at the bar graphs and make deductions
about the data. You can also get information based on these bar graphs. For example, you
can say that the mode is the longest bar if the bar represents the frequency.
Choosing a Scale
We know that a bar graph is a representation of numbers using bars of uniform width and
the lengths of the bars depend upon the frequency and the scale you have chosen. For
example, in a bar graph where numbers in units are to be shown, the graph represents one
unit length for one observation and if it has to show numbers in tens or hundreds, one unit
length can represent 10 or 100 observations. Consider the following examples:
So, if the teacher divides the students into two groups on the basis of this mean height,
such that one group has students of height less than the mean height and the other group
has students with height more than the mean height, then the groups would be of unequal
size. They would have 7 and 10 members respectively.
(ii) The second option for her is to find mode. The observation with highest frequency is
115 cm, which would be taken as mode.
There are 7 children below the mode and 10 children at the mode and above the
mode. Therefore, we cannot divide the group into equal parts.
Let us therefore think of an alternative representative value or measure of central
tendency. For doing this we again look at the given heights (in cm) of students and arrange
them in ascending order. We have the following observations:
101, 102, 106, 109, 110, 110, 112, 115, 115, 115, 115, 115, 117, 120, 120, 123, 125
The middle value in this data is 115 because this value divides the students into two
equal groups of 8 students each. This value is called as Median. Median refers to the
value which lies in the middle of the data (when arranged in an
increasing or decreasing order) with half of the observations
above it and the other half below it. The games teacher decides
to keep the middle student as a refree in the game.
Here, we consider only those cases where number of
observations is odd.
Thus, in a given data, arranged in ascending or descending
order, the median gives us the middle observation.