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For drawing a frequency polygon of a continuous frequency distribution, we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively :
a. upper limits of the classes
b. lower limits of the classes
c. class marks of the classes
d. upper limits of proceeding classes

Solution:

Frequency Polygons can be defined as a form of a graph that interprets information or data that is widely used in statistics.

Abscissa is the x value in the point (x, y), and is the distance of this point along the x-axis, from the origin

Ordinate is the y value in the point (x, y)., and is the perpendicular distance of the point from the x-axis.

Class mark in a frequency distribution is the midpoint or the middle value of a given class.

Therefore, abscissae are respectively class marks of the classes.

✦ Try This: The mean of five numbers is 10. If one number is excluded, their mean becomes 8. The excluded number is :

Consider x1, x2, x3, x4, x5 as the five numbers and one of numbers that is excluded is x5

It is given that

Mean of five numbers = 10

We can write it as

(x1 + x2 + x3 + x4 + x5)/5 = 10

By cross multiplication

x1 + x2 + x3 + x4 + x5 = 150

x1 + x2 + x3 + x4 = 150 - x5

Divide both sides by 4

(x1 + x2 + x3 + x4)/4 = (150 - x5)/4 …. (1)

It is given that

Mean of four numbers = 8

(150 - x5)/4 = 8 from equation (1)

By cross multiplication

150 - x5 = 32

By further calculation

x5 = 150 - 32

x5 = 118

Therefore, the excluded number is 118.

☛ Also Check: NCERT Solutions for Class 9 Maths Chapter 14

NCERT Exemplar Class 9 Maths Exercise 14.1 Problem 22

For drawing a frequency polygon of a continuous frequency distribution, we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively : a. upper limits of the classes, b. lower limits of the classes, c. class marks of the classes, d. upper limits of proceeding classes

Summary:

For drawing a frequency polygon of a continuous frequency distribution, we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively class marks of the classes

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