MARIO F. TRIOLAMARIO F. TRIOLA EIGHTHEIGHTH

EDITIONEDITION

ELEMENTARY STATISTICSSection 2-3 Pictures of Data

Pictures of DataPictures of Data depict the nature or shape of the data

distribution

Histograma bar graph in which the horizontal

scale represents classes and the vertical scale represents frequencies

Figure 2-2

Histogram of Qwerty Word Ratings

0 - 2 20

3 - 5 14

6 - 8 15

9 - 11 2

12 - 14 1

Rating Frequency

Relative Frequency Histogram of Qwerty Word Ratings

Figure 2-3

0 - 2 38.5%

3 - 5 26.9%

6 - 8 28.8%

9 - 11 3.8%

12 - 14 1.9%

RatingRelative

Frequency

Histogram and

Relative Frequency Histogram

Figure 2-2 Figure 2-3

Frequency Frequency PolygonsPolygons

A frequency polygon is created by joining class midpoints of each class of a histogram by line segments.

To complete the polygon, assume a class interval with zero frequency before the first class interval. Connect that point with the next class’s midpoint, and then connect all class midpoints. Assume a class interval with zero frequency after the last class interval.

Frequency Frequency PolygonsPolygons

Ogive (called “o-Ogive (called “o-jive”)jive”)

An ogive is a graph that represents the cumulative frequencies for the classes in a frequency distribution. It shows how many of values of the data are below a certain boundary.

Figure 2-5

Ogive

Dot Dot PlotPlot

A dot chart or dot plot is a chart that is made up of a group of data points plotted on a simple scale. These plots are suitable for small to moderate sized data sets, and can highlight gaps and outliers.

GapsGaps

Figure 2-6

Dot PlotDot Plot

Stem and Leaf Stem and Leaf PlotsPlots

Stem-and-leaf plots are a method for showing the frequency with which certain values occur. To construct a stem plot:

Sort data points in ascending orderThe leaf will contain the last digit of

the number, and the stem will contain all

otherdigits.

Stem and Leaf PlotsStem and Leaf Plots

Stem-and Leaf PlotStem-and Leaf Plot

Raw Data (Test Grades)

67 72 85 75 89

89 88 90 99 100

Stem Leaves

6 7 8 910

72 55 8 9 90 9 0

Pareto ChartPareto ChartA Pareto chart is a bar graph that

helps identify which parts of a data set occur most frequently, and it puts those parts first.

It shows, in descending order and from left to right, the frequency of events being studied.

Pareto Chart

Figure 2-7

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Frequency

Accidental Deaths by Type

Pie Chart

Figure 2-8

Firearms(1400. 1.9%)

Ingestion of food or object(2900. 3.9%

Fire(4200. 5.6%)

Drowning(4600. 6.1%)

Poison(6400. 8.5%)

Falls(12,200. 16.2%)

Motor vehicle(43,500. 57.8%)

Accidental Deaths by Type

Scatter Diagram

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Figure 2-9

Deaths in British Military Hospitals During the Crimean War

Boxplots (textbook section 2-7)

Pictographs

Pattern of data over time

Other Graphs