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Statistics
Summary of Graphical Data Displays |
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Dot Plots
In a dot plot, each value is represented
by a dot placed along a number line.
More than one dot above the same point
means that the value was present in the data value more than once (one
time per dot).
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statistics
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Bar Charts or Bar Graphs
A type of graph that uses bars, placed
vertically or horizontally, to illustrate the frequency of data set
categories. Bar graphs are particularly useful for categorical data
sets.
Bar charts allow for the visual
comparison of data. The bars should be spaced evenly and should be
the same width.
A bar graph is usually drawn with the
bars separated, although sometimes you may see the bars without a
separation.
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statistics
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Histograms
It is easy to confuse a Histogram with a
Bar Chart. While a bar chart displays categorical data, a
histogram displays continuous data. In terms of display, a
histogram is always drawn without any separation between the
bars.
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statistics
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Frequency Polygons
Another type of graphical data display in
the field of statistics, the frequency polygon, uses lines to connect
points that represent frequencies. These points can be equated to
the vertical bars in a histogram or bar graph.
A frequency polygon is particularly
useful because it visually demonstrates the "shape" of the
distribution of the population. That is, trends in the population
may be easily demonstrated with a frequency polygon.
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statistics
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Stem-and-Leaf Displays or Plots
A stem and leaf display is a type of data
plot that divides a data values (numbers) into stems and leafs.
Part of the data value becomes the stem and part of the data value
becomes the leaf.
This type of data display keeps the
actual data in tact but displays it in a better graphical form than a
regular table or list. In addition, it allows large data
sets to be displayed in a more concise form.
Take the following set of data
values: 92, 96, 98, 118, 119, 121, 122, 123, 129, 135, 146, 147,
150. Lets use data value 129 as an example. 129 can be
divided into a stem and leaf in a few different ways. 12 can be
the stem and 9 the leaf (put them next to each other and you get 129),
or 1 could be the stem and 19 could be the leaf.
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| Stem |
Leaves |
| 9 |
2, 6, 8 |
| 11 |
8, 9 |
| 12 |
1, 2, 3, 9 |
| 13 |
5 |
| 14 |
6, 7 |
| 15 |
0 |
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Statistics
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Time Series Graphs
Some data is collected over a period of
time. As a result, statisticians use a time series graph to
examine the behavior of this data over time.
A time series graph must have time on the
x or y axis. Visually, a time series graph may be represented in
many forms, including a histogram or frequency polygon. However, a
frequency polygon or other line graph tend to be favored in making time
series graphs.
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Pie Graphs / Pie Charts
A pie graph or chart is a circle that is
divided into different portions (slices). The size of the slices
depends on what percentage of the data falls into each
"slice," or category.
A pie graph may display both qualitative
and quantitative data. However, a pie graph is particularly useful
and easy-to-use for qualitative data.
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Pareto Charts
A Pareto chart is a form of bar
chart. It is usually used for categorical data. In a Pareto
chart, the horizontal axis represents the categories. The bars,
which represent data frequency, are ordered from largest to smallest so
that interpreting the chart is more convenient.
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