This document discusses different types of statistical graphs used to represent data distributions, including histograms, relative frequency histograms, frequency polygons, ogives, dot plots, stem-and-leaf plots, Pareto charts, pie charts, and scatter plots. It emphasizes that the goal of these graphs is to understand a data set by using a suitable graph that effectively reveals important characteristics like the shape, center, and variation of the distribution. Histograms specifically are highlighted as being important for portraying the nature of a distribution, with normal distributions having a characteristic "bell shape".

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Created by Tom Wegleitner, Centreville, Virginia
Edited by Olga Pilipets, San Diego, California
Overview

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
1. Center: A representative or
average value that indicates
where the middle of the data set
is located.
2. Variation: A measure of the
amount that the values vary
among themselves.
3. Distribution: The nature or
shape of the distribution of data
(such as bell-shaped, uniform,
or skewed).
Overview
Important Characteristics of Data
0
10
20
30
40
50
60
70
80
90
1st Qtr 2nd Qtr 3rd Qtr 4th Qtr
East
West
North

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Created by Tom Wegleitner, Centreville, Virginia
Edited by Olga Pilipets, San Diego, California
Histograms

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Key Concept
A histogram is an important
type of graph that portrays
the nature of the distribution.

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Frequency
Distribution Ages of
Best Actresses
Frequency DistributionOriginal Data

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Histogram
A bar graph in which the horizontal scale represents
the classes of data values and the vertical scale
represents the frequencies

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Relative Frequency Histogram
Has the same shape and horizontal scale as a
histogram, but the vertical scale is marked with
relative frequencies instead of actual frequencies

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Critical Thinking Interpreting
Frequency Distributions
In later chapters, there will be frequent reference to
data with a normal distribution. One key
characteristic of a normal distribution is that it has
a “bell” shape.
The frequencies start low, then increase to some
maximum frequency, then decrease to a low
frequency.
The distribution should be approximately
symmetric.

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
One key characteristic of a normal distribution is
that it has a “bell” shape. The histogram below
illustrates this.
Critical Thinking
Interpreting Histograms

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Recap
In this Section we have discussed
 Histograms
 Relative Frequency Histograms

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Created by Tom Wegleitner, Centreville, Virginia
Edited by Olga Pilipets, San Diego, California
Statistical Graphs

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Key Concept
This section presents other graphs
beyond histograms commonly used in
statistical analysis.
The main objective is to understand a
data set by using a suitable graph that is
effective in revealing some important
characteristic.

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Frequency
Distribution Ages of
Best Actresses
Frequency DistributionOriginal Data

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Frequency Polygon
Uses line segments connected to points directly
above class midpoint values

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Ogive
A line graph that depicts cumulative frequencies
Insert figure 2-6 from page 58

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Dot Plot
Consists of a graph in which each data value is
plotted as a point (or dot) along a scale of values

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Stemplot (or Stem-and-Leaf Plot)
Represents data by separating each value into two
parts: the stem (such as the leftmost digit) and the
leaf (such as the rightmost digit)

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Pareto Chart
A bar graph for qualitative data, with the bars
arranged in order according to frequencies

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Pie Chart
A graph depicting qualitative data as slices of a pie

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Scatter Plot (or Scatter Diagram)
A plot of paired (x,y) data with a horizontal x-axis
and a vertical y-axis

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Copyright © 2007 Pearson Education, Inc Publishing as Pearson Addison-Wesley.
Recap
In this section we have discussed graphs
that are pictures of distributions.
Keep in mind that a graph is a tool for
describing, exploring and comparing data.