Graphic Presentation of a
Frequency Distribution
HISTOGRAM
A graph in which the classes
are marked on the
horizontal axis and the class
frequencies on the vertical
axis. The class frequencies
are represented by the
heights of the bars, and the
bars are drawn adjacent to
each other

Graphic Presentation of a
Frequency Distribution
▪
A histogram shows
the shape of a
distribution.
▪
Each class is depicted
as a rectangle, with
the height of the bar
representing the
number in each class.

Graphic Presentation of a
Frequency Distribution
▪
The horizontal axis
represents all
possible values, and
the bars are
adjacent
to each other to
show the continuous
nature of the data

Graphical Presentation of a
Frequency Distribution
FREQUENCY POLYGON
Consists of line segments
connecting the points
formed by the
intersections of the class
midpoints and the class
frequencies

Graphical Presentation of a
Frequency Distribution
▪
A frequency polygon
,
similar to a
histogram, also
shows the shape of a
distribution.
▪
Class midpoint is the
value at the center
of a class and
represents the
typical values in that
class

Graphical Presentation of a
Frequency Distribution
▪
An advantage of frequency polygon
is that it
allows direct comparison between two or more
distributions.

Cumulative Frequency
Distributions
CUMULATIVE FREQUENCY
POLYGON
Develop a cumulative
frequency distribution,
and portray it graphically
in a cumulative frequency
polygon

Cumulative Frequency
Distributions

Cumulative Frequency Polygon
Observations:
a)
75% of the vehicles
sold earned a profit of
$2,300 or less
b)
60 of the vehicles sold
for a profit of less than
$1,600
c)
56% of the vehicles
sold for a profit of less
than $2,000
(a)
(c)
(b)

A large internet retailer is studying the lead time for a sample
of recent orders. The lead times are reported in days.
Try This
....
a)
How many orders were
studied?
b)
What is the midpoint of the
first class?
c)
What are the coordinates of
the first class for a
frequency polygon?
d)
Draw a histogram
e)
Draw a frequency polygon
Lead Time (days)
Frequency
0 up to 5
6
5 up to 10
7
10 up to 15
12
15 up to 20
8
20 up to 25
7
Total
40