Transcript Looking at Data

Looking at Data
Measurement, time plots, outliers
and other mysteries revealed!
Graphing Data ….
A Geller-Huchra map
showing the distribution of
distant galaxies - this map
(and others like it) have
transformed our
understanding of the
large-scale structure of the
universe
Different ways of presenting the
devastating data on HIV-Aids in
Africa
A “picture” of our active sun – sunspot data since 1750
Perhaps one of the most important
graphs in history!
Getting to know the language…
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Individuals and Variables
An individual is a object described by a datum
 A variable is a characteristic of an individual
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Example: the trees in a forest would define the
individuals. The caliper (diameter) of the
trees would be a variable. The height or
distance from a lake etc etc would be other
variables.
Variables and Distributions…

Variables can be:
 Categorical
 Quantitative
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A Distribution is the range of values that a
variable can take
Different ways to graph data…
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Stemplots
Histograms
Time series
Measurement…
In stats you must always be aware of what
you are measuring and how you are
measuring (ie – what instrument is being
used).
 Measurement always entails error which
implies variation in repeated
measurements.
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Example: look at ex 1.3
Outliers…
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Compare
Mark
McGwire’s
home run
record with
the variation
in light
output from
the star IY
Ursa Majoris
Are there
any outliers
in either?
Some suggestions…
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Read over summary on pages 21-22 and review
as needed
Try Section 1.1 Exercises: 1.7, 1.9, 1.17, 1.31