Topic: Frequency Polygon
Student Name: Kubra
Class: B.Ed. 2.5
Project Name: “Young Teachers' Professional Development (TPD)"
"Project Founder: Prof. Dr. Amjad Ali Arain
Faculty of Education, University of Sindh, Pakistan
1. FACULTY OF EDUCATION
ELSA QAZI CAMPUS
PREPAIRED BY : KUBRA
SEAT NO: 28
TOPIC: Frequency polygon
ASSIGNED BY:
DR. AMJAD ALI ARAIN
2. OBJECTIVE
:
To represent data in frequency distributions
graphically using histograms, frequency
polygons, and ogives.
a] What % of Americans find life dull?
b] What % of Americans are color blind?
c] How many gallons of soda does the average
American drink during a year?
3. GRAPHS
Purpose: To display data to viewer in pictorial
form
Used to: Describe or analyze data
Discuss an issue
Reinforce a critical point
Summarize a data set
Discover a pattern or trend over time
Useful in getting the attention of the audience
4. THREE MOST COMMON TYPES OF GRAPHS
Histogram
Frequency Polygon
Cumulative Frequency Graph (Ogive)
5. HISTOGRAM
histogram: graph that displays the data by
using contiguous vertical bars (unless the
frequency of a class is 0) of various heights to
represent the frequencies of the classes
To construct a histogram:
Draw and label the x and y axes.
Represent the frequency on the y-axis and the
class boundaries on the x-axis.
Using the frequencies as heights, draw vertical
bars for each class.
7. FREQUENCY POLYGON
frequency polygon: graph that uses lines that connect
points plotted for the frequencies at the midpoints of
the classes; frequencies are represented by the
heights of the points
To construct a frequency polygon:
Find the midpoints of each class
Draw the x and y axes. Label the x-axis with the midpoint
of each class then use a suitable scale for the frequencies
on the y-axis.
Using the midpoints for the x values and the frequencies
as the y values, plot the points.
Connect adjacent points with line segments. Draw a line
back to the x-axis at the beginning and end of the graph
(where the next midpoints would be located)
9. THE OGIVE (CUMULATIVE FREQUENCY POLYGON)
ogive: graph that represents the cumulative
frequencies for the classes in a frequency
distribution
To construct an ogive:
Find the cumulative frequency for each class
Draw the x and y axes. Label the x-axis with the class
boundaries. Label the y-axis with an appropriate
frequency (don’t use actual frequency numbers-yields
uneven intervals or classes)
Plot the cumulative frequency at each upper class
boundary
Starting with the first upper class boundary, connect
adjacent points with line segments. Extend the graph
to the first lower class boundary on the x-axis.
10. CONSTRUCTING STATISTICAL GRAPHS- GENERAL
PROCEDURES
Draw and label the x and y-axes
Choose a suitable scale for the frequencies or
cumulative frequencies, and label it on the y-
axis.
Represent the class boundaries for the
histogram or ogive, or the midpoint for the
frequency polygon, on the x-axis.
Plot the points and then draw the bars or lines.
11. DISTRIBUTION
SHAPES
Bell-shaped: single peak and tapers off at either end
Uniform: basically flat or rectangular
J-Shaped: Few data values on the left side and
increases as one moves to the right
Reverse J-Shaped: Opposite of J-Shaped
Right-Skewed: Peak of the distribution is to the left
and the data values taper off to the right (Positively
skewed)
Left-Skewed: Data values are clustered to the right
and taper off to the left (Negatively skewed)
Bimodal: Two peaks of the same height
U-Shaped: Peaks at both ends and decreases