Histograms, Frequency
Polygons, and Ogives
What is a histogram?
A
graphic representation of the
frequency distribution of a
continuous variable. Rectangles are
drawn in such a way that their bases
lie on a linear scale representing
different intervals, and their heights
are proportional to the frequencies of
the values within each of the
intervals.
Uses for a Histogram
A Histogram can be used:
 to display large amounts of data values
in a relatively simple chart form.
 to tell relative frequency of occurrence.
 to easily see the distribution of the data.
 to see if there is variation in the data.
 to make future predictions based on the
data.
Definition: Bin
 The
class size (width of the
rectangles) in a histogram
 X-axis:
range of data sub-divided
into bins
 Y-axis:
frequency
Quick Review of histogram shapes
The frequency polygon is a graph
that displays the data by using lines
that connect points plotted
for the frequencies at the midpoints
of the classes. The frequencies are
represented by the heights
of the points.
Find the midpoints of each class
Find the midpoints of each class
Create a frequency polygon using
the data
Create a frequency polygon using
the data
Cumulative Frequency Graph
(Ogive)
 The
ogive is a graph that represents
the cumulative frequencies for the
classes in a frequency distribution.
Create an ogive
Draw the x and y axis
Plot the points
Assignment
 Read
54
 Do
through example 2-7 on page
Exercise Set 2-3 1-14 on page 57