Looking at DataLooking at Data

Measurement, time plots, outliers Measurement, time plots, outliers and other mysteries revealed!and other mysteries revealed!

Graphing Data ….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…Getting to know the language…

Individuals and VariablesIndividuals and VariablesAn individual is a object described by a datumAn individual is a object described by a datumA variable is a characteristic of an individualA variable is a characteristic of an individual

Example: the trees in a forest would define the Example: the trees in a forest would define the individuals. The caliper (diameter) of the individuals. The caliper (diameter) of the trees would be a variable. The height or trees would be a variable. The height or distance from a lake etc etc would be other distance from a lake etc etc would be other variables. variables.

Variables and Distributions…Variables and Distributions…

Variables can be:Variables can be:CategoricalCategoricalQuantitativeQuantitative

A Distribution is the range of values that a A Distribution is the range of values that a variable can takevariable can take

Different ways to graph data…Different ways to graph data…

StemplotsStemplots HistogramsHistograms Time seriesTime series

Measurement…Measurement…

In stats you must always be aware of what In stats you must always be aware of what you are measuring and how you are you are measuring and how you are measuring (ie – what measuring (ie – what instrumentinstrument is being is being used).used).

Measurement always entails error which Measurement always entails error which implies variation in repeated implies variation in repeated measurements.measurements.

Example: look at ex 1.3Example: look at ex 1.3

Outliers…Outliers…

Compare Compare Mark Mark McGwire’s McGwire’s home run home run record with record with the variation the variation in light in light output from output from the star IY the star IY Ursa MajorisUrsa Majoris

Are there Are there any outliers any outliers in either?in either?

Some suggestions…Some suggestions…

Read over summary on pages 21-22 and review Read over summary on pages 21-22 and review as neededas needed

Try Section 1.1 Exercises: 1.7, 1.9, 1.17, 1.31Try Section 1.1 Exercises: 1.7, 1.9, 1.17, 1.31